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Hi Louise, thank you for your reply and all the information you've shared. I lived in the UK for over a decade, so I know exactly what you mean by permacloud. I wish you clear skies and all the best. Thanks again. Minos

Hi Adam, yes that seems to be the consensus, thank you for pointing that out. Hi Louise, thanks again for replying, very useful feedback. It seems the PDS focuser can't cope with all that length and weight on it. I gather from your comment that the PDS focuser could cope with no flex when you used the TS quick change filter drawer plus DSLR? It seems as though the GSO CC is more suitable for someone imaging with filters or narrowband for the provided extra backfocus, like you said. If one does not intend to though, then it seems the Baader/SW CC will better help avoid any potential flex issues. However, by the sounds of it, the weight of a DSLR alone will probably not flex a fully extended PDS focuser, rendering the potentially better optical quality of the GSO CC still a good candidate. May I ask Louise, did you notice any image quality difference between the GSO and Baader during any of your sessions? Apologies if you answered this elsewhere and I know you said it's been a while, I ask because you have used both.Also good to hear you are enjoying more success with your current setup Thank you again for everyone's time, I feel positively overwhelmed by all of your replies. Minos

Ok, thank you for all your input.

Dear Wim, thank you for sharing this picture, very informative indeed, much appreciated!

Dear Fabien, thank you for your reply and your wishes Great to hear from another user of the SW CC that there is no CA. It seems as though modifications, whether to the drawtube, primary mirror position, or the collar of this CC are still necessary though to deal with the protrusion caused by this configuration. Also great to hear that the the protrusion is avoided with the baader CC. I have the Baader EOS locking ring. Thank you for taking the time to share your notes, much appreciated.

Dear alacant, thank you for your reply, your notes are appreciated. You confirm that in your hands, the GSO CC performed optically better than the baader CC. As for the large backfocus and flexing of the focuser, it seems as though the PDS may be sturdier. However, I would like further confirmation for this from users of the GSO CC, as your point is valid and any optical advantages from the GSO CC would be negated if there is significant flexing. Dear Neil, thank you for your input and your notes on the infrequency in the appearance of the reflections with the SW CC. Although, when that is the case, it will be a nuisance to deal with to some degree. Good to know that you did not notice any CA or bloating. Having looked at pictures taken through the 130pds + SW CC, some of them do appear to me to indeed suffer from these artifacts, but then others do not, notably the images taken by Uranium. However, he reported to have undertaken significant work in order to get it to work at peak performance. Indeed, it seems that mileage does vary with this configuration. Thank you again for your reply. Dear alacant, thank you for sharing a picture of your mystery CC, it has certainly added an extra dimension to the list of candidates. I do not mean to pry, but if you could possibly share any details on this item, it would be very informative for the rest of us, as you are in a more experienced position having tested three of these CC's. You ended your prior post with the word - "perfect", which sounds to me as if you've landed on the right CC for the 130PDS. Please advise if possible, many thanks again.

Thank you for your input, yes I looked it up and the Pentax has 1.46mm extra flange focal distance than a Canon. May I ask, where would you say your focus point lies on the focuer, racked in, midway or racked out? Thanks again. Thank you for all of your input Louise. Hi Alacant, thank you for the photo, it is very useful to see the probable configuration with the TS/GSO CC and how far out the focuser is racked. If I may, you mention that you "wouldn't want to guess..", does that mean you haven't tried to image with this configuration to confirm that the PDS focuser wouldn't hold a DSLR properly without flexing? If this is the case, and it does indeed cause an issue with the GSO CC necessitating the focuser to be racked out all the way meaning it won't hold a DSLR properly, then i'll add it to my list of Cons I made for this CC. Thank you again Louise, it seems the PDS focuser would be able to hold then. If I remember correctly, and just to reiterate - you used your GSO CC with a filter wheel & DSLR, because the GSO CC gave you the nesccessary backfocus to enable this configuration - did you ever experience any flexing or other issues with that kind of load racked all the way out? Thank you all again for your invaluable input.

Greetings everyone from sunny Cyprus and Happy Easter to you all. This is my first post on this great forum. I ordered a 130PDS plus SW 0.9x Coma Corrector from my local astronomy shop and it should arrive in the next 2-3 weeks. However, having read through the entirety of this monumental thread, I’ve come to the conclusion that the SW CC is not my best choice. Since it’s Easter time, I have a few days until Wednesday when the shops reopen to alter my order. The shop manager is being very helpful and is willing to amend my order accordingly. I’m writing to you seeking advice for which coma corrector is the best for image quality, based on users' experience. I’ve gathered the following information from this great thread, the links within it and also from a wider google search. 1) Skywatcher 0.9x CC, 2-element – Pros: reduced focal length for easier guiding and wider field of view. Cons: Internal reflections on bright stars. Chromatic aberrations on mid-sized stars. A focus point which causes a protruding drawtube “chopping” off stars, necessitating the need to either shave the drawtube, move the mirror up, or both. I appreciate the mods made by Uranium to the SW CC, but I’m not looking forward to so much DIY. 2) Baader MPCC MKIII, 2- element - Pros: less to no internal reflections. No change in focal length. Cons: demanding accuracy for correct spacing. Chromatic aberration on mid sized stars. Bloating of stars across the field. Same protrusion in drawtube as above. 3) TS/GSO coma corrector, 4-element – Pros: no internal reflections. No chromatic aberrations. No star bloating. No focuser protrusion. Cons: 14% increase in focal length making guiding slightly harder and also gives a reduced field of view. Please do correct me if I’m incorrect regarding any of the above points. If not, then it seems to me that the TS/GSO is the best option with regards to image quality - no need to change primary position or shave the drawtube and you get a higher quality image with regards to no reflections and no chromatic aberrations. I can deal with the increase in FL/FR and reduction in FOV, no worries. I have another scope for that with a superb FOV. My local shop is happy to order me the GSO CC instead of the SW. If possible, could the above be confirmed by any of you to reassure me of my assessment? I know that Louise has posted often about both the Baader and the GSO, but her comments regarding image quality pertain more so to the Baader. In general, there seems to be much more information on the performance of the SW and Baader, so I’m looking for more info regarding the TS/GSO if possible. Many thanks to all you wonderful people sharing your wonderful experiences of the cosmos in our night sky. Looking forward to your replies. Sincerely, Minos.