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The best coma corrector


Vroobel
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Hi,

I use the Bresser Messier Newtonian 10" F5 OTA and temporarily Sony Nex-6 camera to perform astrophotography. I wrote temporarily, because I will consider the A7 body in future, but cannot be sure. I will also consider a dedicated astro camera with full frame, if my plans succeed.

I would like to ask you which coma corrector is the best for my set. I have read about:
- the GSO/Revelation photo-visual cc (very cheap and quite good value for the money),
- the Baader Mark-III MPCC (photographic) (still not bad price, doesn't change F),
- the Explore Scientific HR cc (photo-visual, helical focuser, excellent correction).

The last one is possibly the best among listed above. Moreover, ES = Bresser, so I would assume that this cc is designed for the ES/Bresser Newtonian telescopes like the Baader 2.25x Barlow lens is designed for the Baader 8-24 Zoom lens... But I found out that every cc causes troubles: some guys experienced issues with their focusers, others ones with back-focus distance of their cameras. And what about the asto camera? Do they cause any problems with the ccs?

Is there any owner of ES/Bresser Messier Newtonian OTA (the best if it's 10" F5) and Sony mirrorless E-mount camera using one of the listed or another coma corrector? 

I'll appreciate every opinion.

Tomasz

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I was using the Baader MPCC III with my Skywatcher 130PDS and was never happy with it. After lots of fiddling around to get the spacing just right, I was then dealing with focuser tilt. Due to the bevelled design of the barrel on the Baader, it was a nightmare to get the thing straight. I tried many focuser attachments, compression rings, etc. Nothing really worked well.

Then by chance I came across one of these for sale, used, on here.  TS-Optics NEWTON Coma Corrector 1.0x GPU Superflat - Even a used one was more expensive than a new Baader but much less hassle. It was literally plug and play for me. I've never been happier and highly recommend it.

Good luck with what you decide to go for. 👍

Edited by Jamgood
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Thank you very much.

Your cc is very similar to the Skywatcher f/4 Aplanatic Super Coma Corrector, its price is also similar (SW is slightly more expensive). Is it the same product?

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6 minutes ago, Vroobel said:

Thank you very much.

Your cc is very similar to the Skywatcher f/4 Aplanatic Super Coma Corrector, its price is also similar (SW is slightly more expensive). Is it the same product?

I believe they are the same but with a different brand name on them. 

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1 hour ago, Vroobel said:

Where is your focus position with the cc in comparison to setup without the cc?

With the Baader, my focus position was very far in. Regardless of the focuser attachment I was using, there was a big chunk of the path taken up by the focuser tube protruding into the OTA, leaving Pacman or D Shaped, stars. (I don't have any images of that set up)

With the TS Optics CC, the focus is pushed outward by roughly 20mm, give or take. My focus point now has no focuser tube protrusion at all. 

focus.thumb.jpg.8ac4c5f9dac56295d4df65b96b74048e.jpg

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That's unbelievable! How it's made, that two items giving similar effects work in different ways... 🤔

The cc suggested by you isn't cheap, but I seen pictures taken with it. It's designed for full frame sensor and even with that stars are sharp around at the edge. 

Is there any way to use it for visual observation as well? I have a quite nice 38mm Erfle eyepiece for wider and brighter DSOs, but it shows the comas perfectly too close of the centre. 

Edited by Vroobel
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It isn't cheap, you are right but I wish I knew about this CC before I bought the Baader. I would've spent the extra and saved myself a lot of confusion and messing around. I got the Baader when I first started Astrophotography and although I did get good results with it, I always had to crop my images because it never gave round stars all the way to the edge. YMMV. Some people are very happy with their chosen CC's. My experience of the Baader was hit and miss drom one night to the next.

As for visual, I have no idea. I've only ever owned the one telescope and I've never put an eyepiece in it and looked through it. People find that strange but I've never had the desire. My viewing site in my garden is surrounded by so much light, I figure it's a waste of time and Astrophotography is all I wanted to do from the get go.

 

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Hi Jamgood, it's me again. 

I have read on the linked page that there is a camera connection through M48 thread in the cc. Does it mean that I have to buy T2 ring as it's not included? Was it ready to work after a purchase? 

Thanks.

Tomasz. 

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44 minutes ago, Vroobel said:

Hi Jamgood, it's me again. 

I have read on the linked page that there is a camera connection through M48 thread in the cc. Does it mean that I have to buy T2 ring as it's not included? Was it ready to work after a purchase? 

Thanks.

Tomasz. 

If you use use a DSLR, you will need a T2 Ring with M48 connection.

I've only ever used mine with the ASI294MC and connection was not an issue right out the box.

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I use a Sony Nex-6 mirrorless camera. I have read that to use the cc with my 1270mm OTA (over 610mm) I need 55mm distance between the M48 thread and the sensor. I have to check how high is my T2-E mount (Sony) adapter and find a proper M48-T2 adapter. There are lot of them in the market, how did you know which adapter you had to buy? 

Thank you for your support :)

Tomasz

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The ASI294MC comes with enough adapters to put any CC at 55mm, as that is the standard for most, so it was literally just plug and play for me. When I had the Baader, I used it with a Canon 60Da. With a Canon, the back focus to the sensor is 44mm. Add a T Ring at around 11mm between that and the CC add it gives you, roughly, 55mm. Maybe a few spacers needed to fine tune.

I have no experience of Sony cameras, sorry. I don't know what that back spacing on the Sony is.  You can measure it though. 

The little marker on the camera indicates the position of the sensor. (Red Arrow) Measure from there to the flange (Orange Arrow) and then you need to make up that distance to 55mm, obviously including a T Ring. So for example, say the sensor to flange distance is 18mm, plus an 11mm T Ring, you would need to make up 26mm before a CC in whatever connection you're using.

Hope that helps a bit.

Sony-NEX-6_top-960x720.jpg.ef7b37bc650386cd07c1b859b186e87f.jpg

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Oh, my friend, your informations are very helpful. Thank you so much for that. I used the camera and didn't realise that there is the marker, but it is there indeed! :D

Should it be exactly 55mm?

Thank you again,

Tomasz

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I think it depends on the cc and the connection. Mine is 55mm at m48.

Baader is 55mm at m42 and 57.5mm at m48. 

You'll just have to double check with whatever you choose and get appropriate spacers in the correct thread to make up the difference. You can get sets of m42 and m48 spacers in all different sizes.

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I checked it right now. My T2-E-mount adapter attached to the camera gives exactly 55mm space, so I think it's made as a standard. Unfortunately it's T2 thread, not the M48. I found 3 small headless screws and detached a T2 ring expecting the M48 one inside, but there is nothing useful. It will be difficult to find proper threated ring for this exact adapter. 

I think I have a choice between looking for another M48-E-mount adapter 36.5mm long and another same aplanatic 4-lens cc with the T2 thread. As the mentioned earlier Sky-Watcher one has also the M48 thread I tried to find the M48-E-mount adapter and found this one: William Optics M48 Wide T Mount For Sony Nex E Series. 

https://www.rothervalleyoptics.co.uk/william-optics-m48-wide-t-mount-for-sony-nex-e-series.html

There is no information about its height on this website nor others, so I guess the height must be a standard. 

Thank you again Jamgood 

Tomasz

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Exactly. In the meantime I found another cheap one from China including a 2" M48 barrel, so I ordered it. It will take longer time to finish my ATM EQ fork mount, so I will check its quality and accuracy without the cc. Its price causes that I have to collect the money.  😒

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