HELP! Coma on stars at Edge of field STILL

[Gerry Casa Christiana]

Gerry

Help! I've edited the thread to reopen it and added my latest picture below  

I have still not got this sorted. Please have a look at this following picture. I have increased the spacing of the coma corrector by 1mm maybe 1.5. Is it possible that the stars on the edge are caused by mirror pinch? I do tend to tighten up a little the screws in my Newtonian could that cause it? It seems to be going outwards in the corners.

Thanks for any advice  

Gerry 

 

 

[richyrich_one]

More spacing is required.

[Gerry Casa Christiana]

Someone said to me less spacing which to me didn't make sense. 

Im buying now!

[Adam J]

Its more spacing.

You need less if they are flattened as opposed to stretched of of the tail points inwards. Take care though you wont need much more spacing 1 - 2 mm can make a big difference.

[Gerry Casa Christiana]

I've ordered from FLO the m48 plus 2 x 2mm spacers. Before I was using m42 so I thought it's a good time to deal also with vignetting  

[richyrich_one]

Do you have a link to the spacers?

[Gerry Casa Christiana]

Yes hold on here it is. Remember though it's for M48 fitting. 

https://www.firstlightoptics.com/adapters/baader-m48-spacer-for-mpcc-iii-coma-corrector.html

Gerry

[richyrich_one]

What t-ring are you using with that?

[Gerry Casa Christiana]

The Skywatcher M48

https://www.firstlightoptics.com/adapters/skywatcher-dslr-m48-ring-adapter.html

[richyrich_one]

I'm pretty sure it won't work. It is designed for use with baader's own protective t-ring.

[Gerry Casa Christiana]

Don't know but the guys at FLO have put this together for me it was completely their suggestion so I imagine it will work  

[richyrich_one]

From the description for the spacer...

An important new addition for the MPCC Mark III accessory, use the full aperture of the M48 thread instead of M42 in conjunction with the Baader protective Canon T-Ring.

 

[Gerry Casa Christiana]

Yes but there might work with the Skywatcher one because it's the same thread BUT I have asked them the question anyway. I'll let you know. 

Cheers

Gerry

[richyrich_one]

There is no thread on the t-ring side. I have one.

[Gerry Casa Christiana]

This one has a thread where I need it anyway? 

[Gerry Casa Christiana]

20 minutes ago, richyrich_one said:

There is no thread on the t-ring side. I have one.

Do you think your is missing the central threaded part? 

 

Thanks

 

[Adam J]

I just used a 42mm spacer on mine to stop the cc screwing all the way into the t-ring.

[richyrich_one]

22 minutes ago, Gerry Casa Christiana said:

Do you think your is missing the central threaded part? 

 

Thanks

 

It's the spacer that doesn't have the thread. It won't screw into the t-ring.

[Gerry Casa Christiana]

Ah yes I see thanks for the heads up. 

So ill need the Baader protective T ring for it to work 

 

Thanks

Gerry

[richyrich_one]

Beware. I have been down this route.

I have both the baader t-ring and spacer. It's designed to work with an internal filter fitted within the t-ring. Without the filter it will be over spaced from the start.

Then it becomes an expensive prospect. I gave up on it and stuck with m42.

What camera/scope are you using? Good flats should take care of vignetting.

[Gerry Casa Christiana]

Thanks

I almost bought it yesterday but in the end changed my mind. It's a bit of a shame though there doesn't seem to be a solution out there. 

Thanks for all your help Rich. I'll stick to the M42. 

Gerry

[richyrich_one]

You're welcome.

If you specify the scope/camera and post an example of the problem perhaps someone can help.

[Gerry Casa Christiana]

I've done that on another thread it's just a spacing issue with comet stars at the edges. I spent most of the day yesterday redoing the focuser (it wasn't quite perpendicular)  anyway then I did the collimation yes of course it has to be offset! Anyway I did it best I could. I have laser etc but it's not as straightforward as all the videos say  

By how much is yours over spaced? Here it says you can use it. Do you know that you have to unscrew the thread from the coma itself and then connect the spacer that's why you could have too much spacing if you look at the second picture the thread is removed  

http://www.baader-planetarium.com/en/2"-mpcc-mark-iii-(multi-purpose-coma-corrector-for-newtons).html

[richyrich_one]

Hope you get it sorted.

[Gerry Casa Christiana]

Help!

I have still not got this sorted. Please have a look at this following picture. I have increased the spacing of the coma corrector by 1mm maybe 1.5. Is it possible that the stars on the edge are caused by mirror pinch? I do tend to tighten up a little the screws in my Newtonian could that cause it? It seems to be going outwards in the corners.

Thanks for any advice  

Gerry