Archive for the ‘SkyWatcher Explorer 130P’ Category

Photographing the Moon with a SkyWatcher Explorer 130P Telescope

Friday, May 28th, 2010

Date: 19th May 2010
Time: 9:30 – 10:15pm
Location: Weston, Hitchin, Herts, UK (about 52o north)
Telescope: SkyWatcher Explorer 130P
Camera: FujiFilm FinePix F200 EXR
Magnification (telescope): 52x (but not really important)
Exposure (camera): Various

This post contains a set of photographs I took of the Moon on May 19, 2010, at about 10pm. All the photos were taken at the same magnification (52x), using my SkyWatcher Explorer 130P telescope and a FujiFilm FinePix F200 EXR compact digital camera. The only variable was the exposure time.

It’s worth pointing out though that the magnification wasn’t really important. This is because the moon is so big that you don’t need to worry about magnifying it very much. The eyepiece I used gave me a magnification of 52x, but I also adjusted the magnification of the camera itself, which would have increased the magnification a bit. Then, in PaintShopPro, I played around with the magnification a bit more to get photos that were a manageable size.

So, basically, I’m not sure what the final magnification is in the photos shown below.

The astrophotography setup I use (telescope, camera and adapter) is described in the post Digital Camera Astrophotography for Absolute Beginners.

Photograph Exposure Time
in Seconds
Photo of Moon with a 1.5 second exposure time 1 1/2
Photo of Moon with 1 second exposure time 1
Photo of Moon with a 1/2 of a second exposure time 1/2
Photo of Moon with a 1/3 of a second exposure time 1/3
Photo of Moon with a 1/4 of a second exposure time 1/4
Photo of Moon with a 1/5 of a second exposure time 1/5

You can see that a 1.5 second exposure produced a photo that was a bit over-exposed. This was also true of the 1 second exposure. Everything below that looks OK though, I think, although the 1/5 second shot looks a bit dark I guess.

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Review of the SkyWatcher SupaTrak Auto Tracking Motorised Alt Azimuth Mount

Wednesday, April 28th, 2010

I bought my SkyWatcher Explorer 130P telescope in March 2009, so I’ve had it for just over a year now (April 2010). One of the reasons I opted for this particular telescope was because it had a motorised mount. I knew nothing about mounts (or telescopes for that matter) at the time so I based my choice on what I had read on the Internet.

Am I pleased with the mount? well, kind of. In this post I’ll share my thoughts on what I like, and dislike, about it.

Good Points

1. Physically connecting the mount to the telescope tube and the tripod is very straightforward and can be done within a minute or so.

2. Setting up the software is also fairly easy to do. There is a one-off  task to set up the latitude for your location, which only needs to be redone if you use the telescope several miles from where the setup is done.  

3.  The setup process for each viewing session is simply a case of switching on the power supply while the telescope tube is horizontal and pointing north. 

4. Tracking objects works well so long as you have carried out steps 2 and 3 above accurately.

Bad Points

1. The battery pack does not have an on/off switch, meaning that you need to use the thumb screw to connect it to, and disconnect it from, the mount.

2. The mount has two servo motors: one for altitude adjustment and one for azimuth (horizontal) adjustment. I find that the azimuth motor seems to struggle sometimes, even when the batteries in the battery pack are new. The problem seems to be worse in the cold weather.

3. My handset broke after I had had the telescope for 11 months (see http://www.myastronomyblog.com/?p=269 for more information).

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Problem with my SupaTrak Alt-Azimuth Mount

Monday, February 22nd, 2010

On Saturday (20th Feb, 2010) I was eagerly looking forward to taking a few more photos of Orion, but I had a nasty surprise when my SupaTrak Alt Azimuth mount refused to play ball.

When I switched on the handset/motorized mount, the Set and Go Cruise buttons starting flashing, and they wouldn’t stop. This rendered the the motorized mount useless as it refused to do anything.

Having put a post on a forum, it looks as though there might be a communication problem between the handset and the mount.

I bought my telescope (a Sky-Watcher Explorer 130P) just under a year ago, so it should still be under warranty if I need to return it. I hope it doesn’t come to that as I don’t want the hassle.

So, it looks as though for the time being I’ll have to revert to my 50mm reflector telescope … oh hum …

Update – 23 February

I put another post on a different forum, again asking the same question and, yes, it looks as though it is a communications problem between the handset and the alt-azimuth SupaTrak mount.

This morning I received an email from Telescope Planet asking me to return the handset. Hopefully, it is that rather than the mount, which would cost a lot more to send through the post.

Update – 04 March

Well, I’m still without a handset, so in effect I’m still without a telescope ! We’ve had some really clear nights recently as well, so it’s all a bit frustrating …

Update – 08 March

Still no word from Telescope Planet … and we’ve had some really clear skies just recently.

Update – 13 March

Today I received a new handset from Telescope Planet … but the problem still exists. I’ve sent another emal to Telescope Planet asking them what to do next. It’s looking as though the mount will need to be replaced.

Update – 18 March

I’m still without a working telescope. I feel frustrated at the moment because, although they are always very polite, I always feel that there is a lack of information from Telescope Planet as to what they are doing to resolve my problem.

I’m also aware that the nights are becoming lighter and I’m losing valuable astronomy sessions while my telescope is broken. I’ve also started looking at alternative telescopes – just in case I end up having to buy a new one. I need this situation with my broken scope to be resolved by the end of the month (March 10).

Update – 23 March

I’ve received an email from Telescope Planet asking me to package up the mount and handset so that they can be sent to the manufacturer for testing/repair. It feels a bit like pulling teeth, but I guess we’ll get there in the end.

Update – 30 March

Today I posted the mount, power supply pack and handset off to Optical Vision (the suppliers to Telescope Planet) so that the unit can be tested and, hopefully, fixed. I guess I just have to wait now.

Update – 08 April

I contacted Optical Vision today to see if they had made any progress with my ‘mount’ problem, but it was still waiting for a technician to test it. They rang me back later though to say that they had tested the mount and it was OK. They spoke to my wife so I’m not sure what was said exactly, but they’re returning everything to me – with another new handset (see 13th March entry above – I’ve been here before).

Anyway, everything should be with me by Monday (it’s Thursday today), so we’ll see.

Update – 16 April

Success – yesterday I received my mount, handset, and battery pack back from Optical Vision, and everything now works OK. The handset has been replaced so that must have been the problem (the replacement handset that Telescope Planet sent me a while ago must have been faulty).

So, in conclusion, a successful outcome even though it has taken eight weeks to resolve the problem. Everyone I have dealt with at Telescope Planet and Optical Vision has been very polite and helpful, although I have been frustrated sometimes by the slow progress.

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Calculating the true field of view

Wednesday, February 3rd, 2010

One of the things that has puzzled me slightly since I bought my telescope a few months ago is this business of apparent field of view and true/actual field of view.

When you look through your telescope, the area you can see is known as the true (or actual) field of view. The field of view of your telescope is determined by the design of the eyepiece of the telescope.

To calculate the field of view you need to first find out the value of the apparent field of view.

Every eyepiece has its own value of the apparent field of view, which is supplied by the eyepiece manufacturer.

Next, work out the value of magnification. To do this, divide the value of the focal length of your telescope by the focal length of the eyepiece. 

For example, if your telescope has a focal length of 650mm (which is the case for a Sky-Watcher Explorer 130P), and your eyepiece has a focal length of 10mm, the magnification for your telescope will be 650 / 10 = 65.

Finally, divide the apparent field of view by the magnification to get the true/actual field of view.

For example, if the eyepiece has an apparent field of view of 50 degrees and a magnification of 65X, then the actual field of view is equal to 50 degrees / 65X = 0.77 degrees.

If the eyepiece has an apparent field of view of 55 degrees and a magnification of 65X, then the actual field of view is equal to 55 degrees / 65X = 0.85 degrees.

So, the greater the apparent field of view, the greater the actual/true field of view will be.

Also note that lower magnifications will give you a greater field of view than higher magnifications.

If you do not know the apparent field of view of the eyepiece, you can get a rough figure for the actual/true field of view by using the following formula:

42/Magnification

So, for the above example, we would get 42/65 = 0.65 degrees.

Field of View Calculator

You can find a field of view calculator here (you need to know the magnification and the apparent field of view):

http://www.dixondevelopment.co.uk/calculators/field-of-view-calculator.htm

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Photographing Mars with a SkyWatcher Explorer 130P Telescope

Monday, February 1st, 2010

Date: 30th January 2010
Time: 6pm
Location: Weston, Hitchin, Herts, UK (about 52o north)
Telescope: Sky-Watcher Explorer 130P
Camera: FujiFilm FinePix F200 EXR
Magnification (telescope): 52x
Exposure (camera): 1/60th of a second

Mars 52x magnification 1-60th second exposure
Mars – 30th January 2010

Here is my second attempt at photographing Mars – still not very successful ! I took a whole batch of photos and this was the best one … it’s a bit tricky this astrophotography.

In the end I had to settle with using an eyepiece that gave me a magnification of 52x. When I increased the magnification upto 130x, I couldn’t find Mars on the LCD screen of my digital camera.

I think one problem is that the camera lens does not align perfectly with the eyepiece when the camera is on the adapter, so if the field of view is not wide enough, the camera can’t see the object even though the object is visible through the telescope itself.

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It’s frustrating sometimes …

Wednesday, January 27th, 2010

Although I really enjoy being an amature astronomer, it can be really frustrating sometimes. Take last night (26th January, 2010), for example …

The sky had been slowly clearing during the afternoon and I knew I was going to be on my own during the evening – my wife had a work-related dinner to go to … great I thought – I can spend as much time in the garden as I want to without having to worry about whether my wife was getting annoyed at being left on her own … again!

I have been desperate to get some good photos of Mars, and this week it’s closer to Earth than it will be for the next couple of years, so I’ve got to get out there soon.

So, at about 7pm I got my Sky-Watcher Explorer 130P out of the shed, along with a selection of eyepieces, and left them outside to get used to the cold (very cold) evening temperature … the sky was still really clear … great!

So, at about 7:30pm I put my coat on, etc and go outside. I look up and, yes, it’s still clear … great!

I then spend the next 10 minutes or so setting up the telescope and camera and, I’m just ready to go when I notice that I can’t see Mars anymore … or the moon for that matter … yes – it’s gone cloudy … s**t !! … I guess I’ll put everything away then … there’s always tomorrow …

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Using a Red Dot Finder

Friday, November 6th, 2009

When I first bought my SkyWatcher Explorer 130P telescope I was intrigued to find out what a red dot (or red-dot) finder was. When I was choosing the scope, I had read that it had a red dot finder, but I had no idea what one was.

What is a red dot finder?

A red dot finder is a zero magnification, battery powered, pointing tool that uses a coated glass window to superimpose the image of a small red dot onto the night sky.

The red dot finder is equipped with an on/off and brightness control switch, along with altitude (up and down) and azimuth (left and right) adjustment controllers.

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Setting up the red dot finder

Before you can successfully use a red dot finder, you need to set it up.

This is a very straight forward process and, providing you don’t bang into the red dot finder and knock it out of alignment, will only need to be done once.

  1. Open the battery compartment by pulling the cover down (you can gently pry it open by using a small screwdriver in the two small slots).
  2. Remove the plastic shipping cover from the battery and replace the cover.
  3. Connect the red dot finder to the telescope.
  4. Turn on the red dot finder by rotating the on/off knob clockwise until you hear a ‘click’. Continue to rotate the knob to increase the brightness level.
  5. Insert a low power (for example, a 25mm) eyepiece into the telescope’s focuser.
  6. Locate a bright object, for example, a distant street light, and position the telescope so that the object is in the centre of the field of view.
  7. With both eyes open, look through the red dot sight tube at the object. If the red dot overlaps the object, the red dot finder is already correctly set up. If it is not, adjust the azimuth and altitude adjustment knobs until the red dot overlaps the object.

Using the red dot finder

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To use the red dot finder:

  1. Turn on the red dot finder.
  2. Look through the sight tube and move the telescope until the red dot merges with the object. You should keep both eyes open while doing this.
  3. Remember to turn off the red dot finder when you’re finished otherwise you’ll run down the battery.

Drawbacks

I guess the only real drawback I find when using the red dot finder is that you need to be able to see the object at which you want to point the red dot finder. This is fine when you want to look at Jupiter, for example, but makes life a bit trickier when the object you’re trying to find is not visible to the naked eye.

Ideally, I would like to also have a normal low power finder scope attached to the main telescope to make life a bit easier from time-to-time.

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Adding some GOTO functionality to a SkyWatcher Explorer 130P telescope

Monday, October 5th, 2009

One of the drawbacks I find with my SkyWatcher Explorer 130P telescope is that, as a novice astronomer, I sometimes fail to find a particular object in the sky. For example, I recently failed to find Uranus (twice) – I knew roughly where it was in the sky, but I just couldn’t see it.

In many ways, that’s all part of the fun, and was my main reason for not buying a GOTO telescope – I wanted to learn how to find objects in the sky without simply relying on a bit of software to find them for me !

However, sometimes I do feel that I could do with a bit of help.

Red Dot Finder

The SkyWatcher Explorer 130P telescope I own is equipped with a red dot finder which, although useful to have, is only of any real benefit for me when I can see (with the naked eye) the object I want to view through the telescope, or something fairly close to it.

Basically, you need to be able to see the object on which you want to place the ‘red dot’;  if you can’t, you have to guess where it is.

It was after my failed attempts to find Uranus that I thought to myself that I must do something to reduce the ‘guessing’ element.

SupaTrak Heavy-Duty Motorised Multi-Speed Auto-Tracking Alt-Azimuth Mount

The SupaTrak motorised auto-tracking mount lets you track an object once you have found it. This, in my opinion, is essential if you want to study an object for a few minutes without needing to continually adjust the scope’s position. But again, this only comes into its own once you have found the object.

Stellarium Software

An essential tool for me as a novice astronomer is Stellarium software, which provides a real time view of the sky. Unless I am going to observe an object I am familiar with, I always have a quick look at the Stellarium software to get my bearings and to identify where objects are in the sky, or where they will be in a few hours’ time (for example).

One of the features of the software is that you can display an alt-azimuth grid on the screen, as shown in the (very rough) sketch given below.

Stellarium grid showing positions of various objects

 

 

 

 

 

 

 

 

The important thing here is that the grid shows the horizontal (left to right) and vertical (up and down) position of an object (not a very technical description I know, but hopefully you’ll understand what I mean).

Now this is interesting because the SupaTrak Alt-Azimuth mount also has a vertical scale.  This means that if I set the position of the mount so that it matches the vertical value from the Stellarium grid, the telescope should be correctly set, vertically, for the object I’m trying to view – the telescope should be set to the correct height.

The only question now is how to set the horizontal value, in other words, how to rotate the telescope around so it is pointing in the right direction for the object.

Creating a Horizontal Scale for the SupaTrak Alt-Azimuth Mount

It seems strange to me that the SupaTrak mount doesn’t have a 360 degree horizontal scale to aid with the positioning of the telescope, so, I decided to add one myself. If you look at the photo below, I have indicated where I have added the scale (the scale isn’t actually shown on this photo – just its position is).

SupaTrak Alt-Azimuth Mount

I created the scale by initially wrapping a piece of string around the mount, in the position where I wanted to put the scale. This enabled me to establish how long the scale needed to be. I then drew the scale on a piece of paper, going from 0 to 360. In fact, I drew the scale in four sections to make it easier to manually handle: 0-90, 90-180, 180-270, and 270-360.

I also put a small mark (line) on the top of one of the tripod legs. This mark has to line up with the telescope when the telescope is pointing North, and must line up with zero on the scale (see photo below).

Finally, I cut out the scale and stuck it in position on the mount  (see photo below).

Using the Scale

To use the scale:

  1. Switch on the telescope and point it in the direction of North, making sure that both the vertical scale (the one that is built into the scope) and the horizontal scale (the one drawn on paper) are both set to zero. So, the scope should be horizontal, pointing North, with both scales set to zero. The mark on the top of the tripod must line up with zero on the horizontal scale.
  2. Turn the telescope off and then back on.
  3. Use the control unit to position the telescope so that it matches the coordinates taken from the Stellarium software.

Tolerance

To maximize the chances of the object appearing in the field of view, you should use a very low magnification eyepiece. If you have a 40mm eyepiece, use that.

Obviously, if the telescope’s starting position is slightly out, for example, if it’s not completely horizontal or it’s not pointing to North, that will have an impact on how successful you are.

SupaTrak Alt-Azimuth Mount - with scale

 

 

 

 

 

 

 

 

 

And here (below)is a close up of the hrozontal scale, showing how zero and 360 degrees need to line up with the line (mark) on the tripod. This is the position that the scale needs to be in when the telescope is switched on.

SupaTrak Alt-Azimuth Mount - with scale - clos up

 

 

 

 

 

 

 

 

 

Obviously, none of this will turn your telescope into a fully blown goto scope, but it may help you to get the scope within a few degrees of the object you’re trying to find.

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A Quick Review of the SkyWatcher Explorer 130P

Friday, August 14th, 2009

Apart from using a small refractor telescope that my wife bought me a few years ago, my SkyWatcher Explorer 130P has provided me with my first real attempt at amateur astronomy.

I bought the telescope at the end of March 2009 and, apart from a gap of a couple of months (when it didn’t get dark until about 11:00pm), I have been using it ever since.

Reality Check

When I first unpacked it I thought wow! – I’m going to get some great views of planets and galaxies through this. Of course, the reality is that to get really good views, like those we see printed in books, you need to move to a completely different level, and a 5-inch reflector is not going to produce the same images as the Hubble telescope does. I found this out the first time I viewed Saturn – I was expecting to see a great big image in my telescope, whereas the reality was a very small (probably about 2mm diameter at x130 magnification) bright ball. I could just about make out (resolve) Jupter’s rings, but that was about it.

SkyWatcher Explorer 130P

I guess it would be lie if I said I wasn’t a bit disappointed in this – I think my kids were as well – my wife certainly was!

OK, so you have to be realistic about what can be achieved with a telescope that costs less than £200, but a few months on I’m getting use to my scope and I really like it.

Eyepieces and Magnification

In addition to the eyepieces that came with the scope (25mm, 10mm, and a Barlow x2), I recently bought a 5mm eyepiece. The focal length of the telescope is 650mm, so I can achieve the following magnifications:

Eyepiece Focal Length (mm) Magnification With Barlow Inserted (x2)
40 x16.25 x32.5
25 x26 x52
10 x65 x130
5 x130 x260

Like many novice astronomers just starting out, I thought I would go straight for the high magnifications, after all, why bother to view something at 65x when you can view it at 260x ? Well, the answer is that at 65x the image may well be much sharper and brighter than at 260x, and I must admit that I find it dificult to get a sharp image at 260x. In fact, I spend most of my time in the 65x to 130x range. After all, a particular telescope can only capture so much light, and if you crank up the magnification too much, the catured light will have to be spread over a larger image, making it less bright and probably a bit fuzzy.

SupaTrak Heavy-Duty Motorised Multi-Speed Auto-Tracking Alt-Azimuth Mount

I love the motorised auto-tracking mount that came with the telescope, even though it has taken me a bit of time to get used to using it. The main problem I have is that I often press the wrong button – sending the scope off in the wrong direction. This is operator error though, and is something I am slowly getting better at handling.

When I was looking into buying the telescope I wasn’t sure whether I needed a motorised mount, but I’m certainly glad that I went for one. It just makes tracking objects in the sky so much easier. Objects move really quickly and if you’re not automatically tracking them, they’ve disappeared out of the scope’s field of view before you know it.

Red Dot Finder

Instead of a finder scope (a small telescope attached to the main scope), the SkyWatcher Explorer has a red dot finder. You use this by looking though the red dot finder scope and placing the red dot directly over the object you want to view. When you then look through the telescope eyepiece you can see the object.

The problem I find with this is that you need to be able to see an object in order to be able to place the red dot on top of it. So, for example, if you’re trying to find a galaxy that is not visible to the naked eye, it’s tricky to know exactly where to place the red dot.

What I tend to do is to use a small pair of binoculars (10 x 25) to find the object, or to find something fairly close to it. I then guess as to where to place the red dot. I find this a bit hit and miss, and given a choice I think I’d rather just have a normal finder scope.

Weight

The SkyWatcher Explorer is fairly light and easy to move about, although my 10 year old son can’t confidently move it, so it’s worth bearing this in mind if you’re looking to buy this scope for a child.

Conclusion

I looked at plenty of scopes (on the Internet) when I was looking for my SkyWatcher Explorer, and I’m pretty pleased with my purchase. Of course, like everyone else, I would like something better, but you have to look at the practicalities of what you want out of your scope, where it is going to be stored (eg can you easily move it outside when you need to). Also, when you’re buying your first scope you don’t know whether it’s a hobby that you’ll be into for a few weeks, months, or years, so it’s probably best not to blow £2000 on your first purchase!

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Welcome to My Astronomy Blog

Wednesday, August 12th, 2009

Welcome to my astronomy blog.

My name is John Dixon and I am a novice astronomer. My main telescope is a SkyWatcher Explorer 130P reflector, which I recently bought (April 09). I also have a 2-inch refractor, which my wife bought me a few years ago, and a couple of pairs of binoculars.

April isn’t a particularly good time of the year in which to get into astronomy as the nights are pretty light at this time of year. Anyway, I played around with the scope until the end of May, and then I had a couple of months off. It’s now August and I’m keen to get back out into the back garden to do a bit of star gazing.

I intend to use this blog as a way to record my viewing sessions. I’m not an expert, so I’ll probably say a few, or a lot, of stupid things. But that doesn’t matter – it’s all just a bit of fun!

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