Advice on multiple upgrades for SCT

[lucid]

There are a few improvements I wish to make to my CPC Deluxe HD 800. Before I go ahead and make any mistakes in buying the wrong pieces, I wonder if you might give some guidance.

 

I would like to make focusing easier and am considering the “MoonLite CS Dual Rate SCT Crayford with 2 inch thread”. Am I correct that this will replace the 1.25 inch visual back that came with the telescope. And will that also require a 2 inch diagonal or can I continue using a 1.25 inch until I can afford to upgrade that as well?

 

Also, in the future I have thoughts of mounting another scope on top of the SCT - a guidescope or other refractor. I understand this would require the CGE dovetail bar to be in place, but then there is the problem of the finderscope on my 8 inch scope? Is there a different finderscope or other arrangement that can accommodate all of these attachments? In fact, on the other side of the SCT tube, probably sooner than I purchase a guidescope, I would love to mount a camera and I’ve seen that there is a Celestron piggyback camera mount. Will this also be possible on my SCT? And if it is possible, should I be concerned about the balance of weight on the scope now?

 

And one further thing, I have the 9x50 finderscope which gives me an upside down image. I see that the back lens can be unscrewed, so is there a replacement that can give a normal upright image?

 

 

Thanks for any and all advice.

[PeterCPC]

I had a CPC800XLT. I put on a piggy back mount - no problem with weight - most of the weight is in the camera. Make sure you use the correct screws!

I agree the focuser is not up to much - I have installed a Starlight Feathertouch Microfocuser on my C9.25 and it's brilliant. I did install a Revelation Dual Crayford focuser on the CPC but removed it again as the weight was too great and it sticks out way past the visual back adding to the weight issue and restricting severely the latitude of the scope.

Hope that helps a bit.

Peter

[lucid]

My concern re weight of camera is whether this will affect the tracking of the telescope - depending on which dslr and lens combo there can be a sizeable weight, just ask my wrist!

I had read that focusing with a crayford has the advantage on not shifting the image. I assume that will still be a problem even using the feather touch microfocuser?

[Guest]

My concern re weight of camera is whether this will affect the tracking of the telescope - depending on which dslr and lens combo there can be a sizeable weight, just ask my wrist!

I had read that focusing with a crayford has the advantage on not shifting the image. I assume that will still be a problem even using the feather touch microfocuser?

Hi,

You really need to consider getting a weight balance system in place on your scope, if you add anything like a guide scope, your tracking will be terrible without balance and it will put massive strain on the worm gears in the mount.

Even with a DSLR hanging on the back you need to balance it perfectly, trust me as I have been there it makes a huge difference I can't stress that enough, I can get 20 min subs out of my 8" SCT, with perfectly round stars.

It really is worth spending the money on a good rail with weights that can be moved forward and backwards along the scope, and be moved closer and further away from the tube on what is known as a 2D balance system.

Hope that helps

MM

[lucid]

I thought so, thanks. Can you point me in the direction of something that might be suitable for my telescope setup...?

[Guest]

I thought so, thanks. Can you point me in the direction of something that might be suitable for my telescope setup...?

This is what I use on my scope, but you may need extra weights I have one 2.2kg weight on mine, and works fine, I set it up in my garage and balanced all my se ups one at a time, and put marks on the rails so I can swap between set ups and move the weight to the correct position each time.

http://www.rothervalleyoptics.co.uk/adm-mini-dovetail-system-counterweight-kit.html

Also for help on balancing see here

http://jan.eaglecreekobservatory.org/balance.html

MM

[PeterCPC]

I agree with the above but also must stress that you need to consider how what you add may affect the angle that the scope can go to without hitting the mount. The CPC800 does not give much space once you start adding gear on the back - another reason not to use the Crayford focuser, it's a lot of weight but it's also quite deep from front to back. The microfocuser does not add anything at the back. Whilst it's true that the Crayford does not shift the image because it's in place of the visual back, I don't think that the microfocuser should be a problem in itself but you can still get mirror flop. It's a compromise in the end. I must say that when I had my CPC it could cope with being out of balance by about 1lb without affecting the GOTO i.e. Canon on the back and dew shield on the front.

Peter

[GuillermoBarrancos]

The CPC800 EdgeHD Deluxe has Mirror Lock, so Mirror flop / image shift should not be much of an issue compared to the regular SCT's.

So to improve focusing, you can just go for the micro focuser replacement, instead of putting a heavy focuser on the Visual back.

http://www.firstlightoptics.com/starlight-instruments-feather-touch-sct-microfocusers.html