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The Jackal

Which Baadar must i get for Comma Correcting

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Hi Guys

I desperately need advice on selecting a Coma Corrector for my telescope.

I have a GSO 8" F/5 Reflecting Newtonian and I badly need a Comma Corrector for it.

My options are as follows and I don't know which one is best for me and also which adapters to get with it as I only use my scope for Astrophotography.

Options:

Baader Planetarium Coma Corrector Set

http://eridanusoptics.com//store/index.php?main_page=product_info&cPath=167_20_25_146&products_id=621

Baader Planetarium Multi-Purpose Coma Corrector

http://eridanusoptics.com//store/index.php?main_page=product_info&cPath=167_20_25_146&products_id=824

Baader Planetarium RCC I Rowe ComaCorrector with Backfocus

http://eridanusoptics.com//store/index.php?main_page=product_info&cPath=167_20_25_146&products_id=1845

and finally the

Baader MPCC Mk-III Photo-Visual set

http://telescopeshop.co.za/shop/index.php?main_page=product_info&products_id=689

I am very confused on so many options and also if I get one which accessories to get with it to make my Canon 700D fit to the telescope.

Any advice and help will be appreciated.

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The mpcc in the pic looks like the mark ii, the mark iii has grey print not green. Difference is I believe that the mark ii works till f4.5 and the new mark iii for even faster scopes, so both might be ok for you

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The Mark III has a wider illuminated field and is good to f/3.5, better than the earlier version.

You will need a large set of spacers to adapt it to every eyepiece for coma correction and to use 1.25" eyepieces with it.

To figure that out, once you have one eyepiece perfectly corrected, you freeze your focuser and then add whatever spacers are necessary to each eyepiece to make that eyepiece focus at the same place (or as close as you can).  Write down the spacers necessary with each eyepiece and add them before threading on the MPCC-III to the eyepiece.

It only takes a few minutes if you have only a handful of eyepieces.

The TeleVue Paracorr and Explore Scientific HRCC function like a barlow--you insert the eyepiece, and then you dial the top to focus to find the correct position of the top for best coma correction, after starting out with one eyepiece that is set perfectly.

Note that all coma correctors, once one eyepiece is adjusted to the perfect position for best coma correction, are adjusted to allow all the eyepieces to focus at that same point.

This puts the coma corrector the same place in the light cone for every eyepiece and all that is varied is the distance of each eyepiece to the coma-correcting lens. 

It's really nice that they all "parfocalize" your eyepiece set.  After adjusting mine, I found i could get by with about 3mm of focus travel for all my eyepieces, so I went to a shorter drawtube.

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If you can afford a Paracorr then get one. They are very good. I've had the old and new MPCC and I wish I had never wasted money on the Baader's.

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It may well be interesting to hear which eyepiece you are using. I have a faster scope than you at F4.3 and using various Panoptic 68 degree eyepieces the coma is nowhere near as bad as I thought it may be. However change to Meade SWA 24mm a direct match for the Panoptic and the story is not the same, you could be seeing astigmatism and not so much coma as you think. This test was done without Paracorr.

I do use a Paracorr Mk1 by TV and it is excellent but even S/H in the 150 quid area.

Alan.

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