Anyone used an ASI120 with a 200P and a filter wheel? (long shot)

[Fordos Moon]

Perhaps another Stupid Question of the Week contender...

Just asked Zoltan of the excellent 365astronomy.com this question and wondering how i might make things work without being short of back focus. I will be out experimenting with what i do have as soon as the weather permits but thought might be able to get a heads up!

Excited enough embarking on using the ASI120MM alone, I am having thoughts about getting the best results imaging planets using my 200P and if the addition of a filter wheel for colour images is a possibility. The thought is I wouldnt have enough back focus. The addition of 1 5x powermate would be far too much, perhaps the 2.5x one would work?

If anyone has had any success with this set up I would love to hear about it.

[ardbeg74]

Hi Fordos,

I dont have a 200 dob and my scope doesnt have the crayford, but what i can say was back focus was the exact opposite problem for me.

With this filter wheel http://www.firstlightoptics.com/filter-wheels/manual-5-position-filter-wheel.html

I struggled to get inward focus with the supplied nose piece. I was around 15mm or so short of travel. What i had to do was unscrew the nose piece ( or should that be tail piece ) and also unscrew the 1.25" ep adapter on the focuser tube and screw the filter wheel directly on.

Granted i was using a 25 and 10mm ep and not a camera. (My asi 120mm is due to be delivered this week)

Not tried it with the barlow yet, but once the cam comes will let you know how much back focus is required. My gut feeling is that there should be enough back focus. But my main worry is whether i will be able to use the asi in prime focus... the asi has 14mm from thread to ccd so i might just make it!

Hopefully one of the experienced imagers can comment though. Would have thought the 5x might be pushing it... 2.5 should give around 200px of jupiter at the moment. Though perhaps the 5x would be ok with mars??

HTH

Mark

[Fordos Moon]

Hi Mark, and thanks very much for the reponse! I have responded to your message also.

I guess experimentation is the key, and I will keep you informed of any progress I make - soon as the weather clears up!!

regards

Bob

[Fordos Moon]

Hi all, just wondering since time has past since I posted this thread if anyone has successfully used a ZWO ASI120MM, filter wheel and 200P without any inward focus or backfocus issues. I really want to get a filter wheel but have concerns I will not be able to get focus and I don't really want to shell out £150 for this to be the case.

[SnakeyJ]

In focus was my issue with the 200p and stock synta focuser. I got an m57 to 2" compression adaptor from Bern at MA and a 2" nosepiece to male T2 which fits directly to the fw. The other side of the fw is a T2 to 1.25" compresion fitting. Works with everything bar my 2.5x Revelation barlow and is good and solid.

The pds should have a bit more in focus and a bigger margin of comfort.

Insufficient out focus has never been an issue - though can always be cured with some extension.

typed on my mobile with Tapatalk

[Fordos Moon]

In focus was my issue with the 200p and stock synta focuser. I got an m57 to 2" compression adaptor from Bern at MA and a 2" nosepiece to male T2 which fits directly to the fw. The other side of the fw is a T2 to 1.25" compresion fitting. Works with everything bar my 2.5x Revelation barlow and is good and solid.

The pds should have a bit more in focus and a bigger margin of comfort.

Insufficient out focus has never been an issue - though can always be cured with some extension.

typed on my mobile with Tapatalk

Thanks Jake! Is MA Modern Astronomy? How much did the fix it bits cost you? PDS? You have very similar equipment to me! Would you possibly be able to take a photo of the set-up?

[JamesF]

You may well find that a filter wheel would screw straight onto the end of the focuser, and the camera will screw straight to the back of the filter wheel.  There are a few filter wheels that are only about 10mm deep, so that might be sufficient.

Unless you have a tracking dob however I think you might be on a hiding to nothing trying to do mono imaging with it.  If it isn't a tracking dob it might be a whole lot easier to get a set of tube rings and put the OTA on the HEQ5.

James

[Fordos Moon]

You may well find that a filter wheel would screw straight onto the end of the focuser, and the camera will screw straight to the back of the filter wheel. There are a few filter wheels that are only about 10mm deep, so that might be sufficient.

Unless you have a tracking dob however I think you might be on a hiding to nothing trying to do mono imaging with it. If it isn't a tracking dob it might be a whole lot easier to get a set of tube rings and put the OTA on the HEQ5.

James

It's on the HEQ5 James! Looks a beast on it! Was looking at the ZWO MFW but it's 19mm I think can you recommend a 10mm one? Am

Looking to get the Baader filters once I sort the wheel out.

Thanks for response!

[catman161]

I use a 200P with a 4x powermate for planetary in an NEQ6. However I use the ASI120MC so no need for a filter wheel.

I did initially have issues with back focus but combatted this by fitting a low profile moonlite focuser with a 50mm draw tube. The other things you can do (which you probably have already) are break the powermate down to its smallest size and use the M42 thread adapter to screw the camera directly to the powermate. This decreases the amount if back focus needed to achieve focus.

Sent from my iPhone using Tapatalk

[Lonestar70]

Hi,

This is relatively easy to determine.

Fit the camera as normal to your scope and bring an image to focus (any starfield will do)

Measure the length of exposed focuser draw tube ( from where it exits the focuser body to the front face of the camera adaptor).

Make a note of this dimension.

Consult the specs of any of your prefered filter wheels and determine the length each one adds to the focal train.

Providing this length (plus say 5mm focus margin) is less than the measured length you wrote down then you will be able to reach focus with it.

Any that exceed the noted length will be unsuitable.

Hope this helps.

Best regards.

Sandy.

[Fordos Moon]

Hi,

This is relatively easy to determine.

Fit the camera as normal to your scope and bring an image to focus (any starfield will do)

Measure the length of exposed focuser draw tube ( from where it exits the focuser body to the front face of the camera adaptor).

Make a note of this dimension.

Consult the specs of any of your prefered filter wheels and determine the length each one adds to the focal train.

Providing this length (plus say 5mm focus margin) is less than the measured length you wrote down then you will be able to reach focus with it.

Any that exceed the noted length will be unsuitable.

Hope this helps.

Best regards.

Sandy.

Thanks very much Sandy, I understand how to work it out now (!) so will do this next time its clear!

[SnakeyJ]

Thanks Jake! Is MA Modern Astronomy? How much did the fix it bits cost you? PDS? You have very similar equipment to me! Would you possibly be able to take a photo of the set-up?

Fordos,

Sorry I missed this reply this morning.    Correct with Modern Astronomy, Bernard is very knowledgeable/helpful and will take the time to discuss options if you give him a call.     Image of the current image train below:

 

My Revelation 5x barlow was causing some reflection/ghosting issues, so I've currently got the Baader x2.25 zoom and huge extension tube - but this gives quite a useful range between x3.2 and x4.5 with the QHY.   The 5x looked a lot neater though, and hopefully I can strip it and resolve or will replace next month with a good 4-5x.

The M57-2" compression adaptor is the third item down this page - http://www.modernastronomy.com/accessories.html#accAdapters

I also brought the TS Low profile T Thread to 1.25 adaptor, sixth item down.

Adaptors get quite expensive quickly, so I've sourced a few bits on ebay and SGL classifieds - you can never have enough!

[JamesF]

It's on the HEQ5 James! Looks a beast on it! Was looking at the ZWO MFW but it's 19mm I think can you recommend a 10mm one? Am

Looking to get the Baader filters once I sort the wheel out.

The Xagyl filter wheels are relatively narrow I think, but I'm sure there are smaller.  I'm struggling to remember who makes them at the moment, but I'll keep looking.

James

[SnakeyJ]

Ian King sells the Xagyl filter wheels - there's a CN review somewhere. I think the manufacturer is Canadian.

typed on my mobile with Tapatalk

[SnakeyJ]

Found the review here at http://www.cloudynights.com/item.php?item_id=2737

[Fordos Moon]

Fordos,

Sorry I missed this reply this morning.    Correct with Modern Astronomy, Bernard is very knowledgeable/helpful and will take the time to discuss options if you give him a call.     Image of the current image train below:

2014-04-06 16.00.29.jpg 2014-03-22 14.06.30.jpg

My Revelation 5x barlow was causing some reflection/ghosting issues, so I've currently got the Baader x2.25 zoom and huge extension tube - but this gives quite a useful range between x3.2 and x4.5 with the QHY.   The 5x looked a lot neater though, and hopefully I can strip it and resolve or will replace next month with a good 4-5x.

The M57-2" compression adaptor is the third item down this page - http://www.modernastronomy.com/accessories.html#accAdapters

I also brought the TS Low profile T Thread to 1.25 adaptor, sixth item down.

Adaptors get quite expensive quickly, so I've sourced a few bits on ebay and SGL classifieds - you can never have enough!

Thanks for taking the time to post the images! A picture paints a thousand words! Im gonna connect stuff up tonight (WILL be clear between 9-11pm!) and measure how much play I have with focusser with just ASI attached :-) as per post above

[Fordos Moon]

Hi,

This is relatively easy to determine.

Fit the camera as normal to your scope and bring an image to focus (any starfield will do)

Measure the length of exposed focuser draw tube ( from where it exits the focuser body to the front face of the camera adaptor).

Make a note of this dimension.

Consult the specs of any of your prefered filter wheels and determine the length each one adds to the focal train.

Providing this length (plus say 5mm focus margin) is less than the measured length you wrote down then you will be able to reach focus with it.

Any that exceed the noted length will be unsuitable.

Hope this helps.

Best regards.

Sandy.

Sandy - am out in observatory now - the length of exposed (shiny silver) focus tube is 1.9mm?!

[Lonestar70]

Sandy - am out in observatory now - the length of exposed (shiny silver) focus tube is 1.9mm?!

Hi,

I think that answers your question... no way you can use a filter wheel with that scope/focuser. 

Changing to a low profile focuser would possibly buy enough extra distance, but not guaranteed.(possibly 12-15mm)

A x 2 or x 3 Barlow would bring the focal point further out, however, the image would be less bright, requiring much  longer exposures.

You could move your primary mirror up the tube towards the focuser say 20mm, this would move the focal point of the focuser out further, but, it may give you issues when using eyepieces... unfortunately, you would also get a small reduction in image brightness, since the small secondary mirror of the 200P would mean some of the light would not be reflected into the focuser.

This is what SW do with the 200PDS which also has a low profile focuser, however, they also fit a slightly larger secondary mirror to enhance the image quality for camera work.

The only other suggestion would be to use your ED 80 since this will have plenty of space available, as you would normally use a 2" long straight extension (in place of the diagonal) for camera use, so just replace the 2" extension with a filter wheel and shorter extension to make up the difference. (not quite so easy with the FF/FR attached, but still possible... (in this case you would have exactly 55mm (critical) distance to play with from rear element of FF/FR to camera focal plane)... great for DSO's but not so good for planetary.

I can't see any real easy answer for your 200P.

Hope this is of some help.

Best regards.

Sandy.

[JamesF]

I think it's worth trying with a decent multiplier barlow.  3x or even 4x is not extreme with this scope at all.  That *might* buy you a fair bit of travel.

James

[Lonestar70]

Hang on a minute,

Those pictures were not there when I did my last post.

Sandy - am out in observatory now - the length of exposed (shiny silver) focus tube is 1.9mm?!

The picture captions say 19mm not 1.9mm

What are those big BLACK things ? it looks like you have got some long extensions fitted... or is one of them a tele extender or some such?

Can you not fit the camera directly into the focuser tube with a short nose piece on the camera?

So what is what on your pictures?

Best regards.

Sandy.

[JamesF]

Yes, I think some clarification is in order  Did you mean 1.9cm?

James

[Fordos Moon]

Sorry I suddenly thought it would be a good idea to put some pics on - you answered quickly lol but much appreciated both of you chaps! The things in order from the scope are an adaptor which I presume is two inch to 1.25 inch, then a 2.5mm powermate and then a kinda nose piece which fits in to the asi to fit it to two the powermate. And yes it's 19mm sorry it was cold out there! So I guess I can lose a lot of the black things lol. Thanks Sandy and James for your extreme patience!!

[Fordos Moon]

I feel I have been somewhat silly with the black things.

[JamesF]

Well, it's going to be, err, interesting

I'd bet you could find a filter wheel that would screw directly onto the end of the focuser tube, but then you'd still need the space in the other side for the powermate.  Alternatively you'd probably be able to put the filter wheel between the powermate and the camera and lose the camera nosepiece.

I'm sure it's possible to get it to work, but I think it will involve experimentation and perhaps more money  For example, you could use a 2" powermate in the focuser with the T2 thread exposed, then the filter wheel and camera (though I'd probably go for the 4x powermate in that case).

James

[Fordos Moon]

Wowsers thanks James I need to do some thinking about my approach here! Will see what all the connections are like tomorrow!