Recommendation please - OAG + Coma Corrector for Nikon DSLR

[MikeODay]

Hi

Does anyone feel able to recommend an OAG + Coma Corrector combination that achieves the correct spacing and good reliable results when connected to a Nikon DSLR?

Cheers

Mike

[kalasinman]

The flange to focal plane distance of a Nikon is 46.5mm as opposed to a Canon at 44mm, thus it may make the use of a thin OAG more important. I doubt there is a perfect off the shelf solution. The Baader Mark II MPCC has no net effect on FL. If your OTA has a low profile focuser you may be ok. I had to cut 15mm off my OTA and move the mirror up to get focus. Easy enough. Some folks get by running the cell adjustment all the way forward. YMMV

[MikeODay]

Thank you for that. I have a Baader MPCC and I'm told I won't be able to get that to work with an OAG fitted to a Nikon. I think you are right - I will need a thin OAG. I'm still not sure about the coma corrector I should buy. The Baader RCC will apparently work if I can get the adaptors I will need but some threads seem to inicate that collimation and/or tube flex is a problem with the RCC.

[kalasinman]

If you have a Baader MkII that's all you need. I believe it will screw to the nosepiece of the t-ting and then drop right in the eyepiece tube of the focuser. I figured my focal distance using calibration marks on my focuser body.

[MikeODay]

Thanks. I have the mk3 and I also want to use an off axis guider at the same time. The problem is that the OAG fits between the coma corrector and the camera and this makes the coma-camera separation too large for the mk3.

It seems I will need to get a different coma corrector together with an OAG and adaptors and I was looking to see if someone has already done this. Are you saying that if I can find a mk2 it will work with an OAG and Nikon?

Cheers

Mike

Edited May 2, 2015 by mike005

[laser_jock99]

What you require is a low profile M48 to Nikon mount adaptor like this

http://www.teleskop-express.de/shop/product_info.php/info/p6527_TS-Optic-ultrashort-Adapter-from-M48-to-Canon-EOS-EF-Bayonet---only-1-mm-optical-l.html

....but for Nikon.  I found one but can't for life of me find a link for it!

EDIT- the other possibility is a coma corrector with longer back focus distance like the  Baader RCC 1 Newtonian Coma Corrector

http://www.teleskop-express.de/shop/product_info.php/info/p6527_TS-Optic-ultrashort-Adapter-from-M48-to-Canon-EOS-EF-Bayonet---only-1-mm-optical-l.html

Edited May 2, 2015 by laser_jock99

[MikeODay]

Thanks for that.

I've been told that the currently available range of OAGs an 55mm back focus coma correctors won't work - even with a "zero" width mk48 adaptor

I'm looking into the RCC - although I have found a number of threads where people describle problems they have had with its sensitivity to sensor alignment / tube flex.

I hope to pick up a set of new Losmandy tube rings that are designed to work with my Orion Short-Tube 80 guide scope to hold the orion guide camera in firm alignment. I'm hoping that this will reduce my differential flex issues enough that I can live without an OAG.

[kalasinman]

Thanks. I have the mk3 and I also want to use an off axis guider at the same time. The problem is that the OAG fits between the coma corrector and the camera and this makes the coma-camera separation too large for the mk3.

It seems I will need to get a different coma corrector together with an OAG and adaptors and I was looking to see if someone has already done this. Are you saying that if I can find a mk2 it will work with an OAG and Nikon?

Cheers

Mike

Mike, I just re-read the info on the Baader MkIII. I says it extends focal distance by 10mm. The Orion TOAG is 10.5mm so seems like your in the ballpark.  Right?

[Xplode]

What you require is a low profile M48 to Nikon mount adaptor like this

http://www.teleskop-express.de/shop/product_info.php/info/p6527_TS-Optic-ultrashort-Adapter-from-M48-to-Canon-EOS-EF-Bayonet---only-1-mm-optical-l.html

....but for Nikon.  I found one but can't for life of me find a link for it!

EDIT- the other possibility is a coma corrector with longer back focus distance like the  Baader RCC 1 Newtonian Coma Corrector

http://www.teleskop-express.de/shop/product_info.php/info/p6527_TS-Optic-ultrashort-Adapter-from-M48-to-Canon-EOS-EF-Bayonet---only-1-mm-optical-l.html

A low profile M48 isn't possible for Nikon because of the smaller flange, it seems to be barely large enough for a low profile M42 at 44mm throat. Canon has 54mm throat.

Thanks for that.

I've been told that the currently available range of OAGs an 55mm back focus coma correctors won't work - even with a "zero" width mk48 adaptor

I'm looking into the RCC - although I have found a number of threads where people describle problems they have had with its sensitivity to sensor alignment / tube flex.

I hope to pick up a set of new Losmandy tube rings that are designed to work with my Orion Short-Tube 80 guide scope to hold the orion guide camera in firm alignment. I'm hoping that this will reduce my differential flex issues enough that I can live without an OAG.

You are correct that a Nikon won't fit an OAG at all with with a 55mm backfocus.

Canon would work with a TS slim OAG, but a Nikon allows 1.5mm less distance between the flange and coma corrector so there is just no space.

If you want this to work you should get a Canon camera...they are much more flexible for astronomy and will cause much less frustration

[kalasinman]

I have a similar satup If I use my current train and insert the MKII between the front of my parfocl spacer (8mm plus 1mm t-adapter) and the back of the TOAG  I get 55.5mm.

[Thalestris24]

Hi

You might be able to get an oag to fit behind a gso F4 coma corrector e.g. from Teleskop Express or from Ian King. I have one of these with a Canon 1100d and filter drawer on an (originally) F5 130pds and it works well. The cc has a backfocus of about 75mm and it increases fl by 10%.

Louise

[kalasinman]

Yes , this seems to be the solution

Hi

You might be able to get an oag to fit behind a gso F4 coma corrector e.g. from Teleskop Express or from Ian King. I have one of these with a Canon 1100d and filter drawer on an (originally) F5 130pds and it works well. The cc has a backfocus of about 75mm and it increases fl by 10%.

Louise

This CC will screw directly into a TOAG.  As this eliminates a 2mm T-ring, total backfocus now 66mm.  In my case I needed an 8mm spacer to get the Nikon and  QHY5L-II mono parfocal, but this still gives 66mm. BTW my Nikon camera adapter is only 1mm and fits very nicely.

I have no interest in using a filter wheel with a DSLR, but with eliminating the 8mm spacer for the wheel, it could fit?

What about vignetting, Louise?

[Thalestris24]

Yes , this seems to be the solution

This CC will screw directly into a TOAG.  As this eliminates a 2mm T-ring, total backfocus now 66mm.  In my case I needed an 8mm spacer to get the Nikon and  QHY5L-II mono parfocal, but this still gives 66mm. BTW my Nikon camera adapter is only 1mm and fits very nicely.

I have no interest in using a filter wheel with a DSLR, but with eliminating the 8mm spacer for the wheel, it could fit?

What about vignetting, Louise?

Hiya

I have a modded 1100d so thought I'd experiment with the filter drawer just for Halpha really but haven't actually put it to much use yet. The filter drawer takes up about 15mm so I think an oag could fit in its place ok. With everything using M48 I don't notice any vignetting The cc lengthens the focal length of the 120pds to 715mm but slows the scope to F5.5. The cc spacing isn't as critical as some and seems to give maybe 3 or 4 mm latitude which might be useful.

Louise

[kalasinman]

Louise, by my figures (always suspect ;-) ) an Orion TOAG and your drawer would put you at 70.5mm with your Canon. Listed backfocus is 70mm. You might have to add a C extension in front of your guide cam to get parfocal.

[Thalestris24]

Louise, by my figures (always suspect ;-) ) an Orion TOAG and your drawer would put you at 70.5mm with your Canon. Listed backfocus is 70mm. You might have to add a C extension in front of your guide cam to get parfocal.

Hi

I actually have an oag I got off ebay However, I've no plans to fit it to the 130pds. But I might try it with the 150pds+qhy8l+mpcc which has been in 'dry dock' for a while.

Louise

[SteveBz]

On 13/05/2015 at 03:21, kalasinman said:

BTW my Nikon camera adapter is only 1mm and fits very nicely.

Sorry this is such an old thread, but do you remember where you got this?

[SteveBz]

On 30/04/2015 at 11:04, MikeODay said:

Hi

Does anyone feel able to recommend an OAG + Coma Corrector combination that achieves the correct spacing and good reliable results when connected to a Nikon DSLR?

Cheers

Mike

Hi Mike,

Did you ever get this sorted? My main camera is a Nikon D5000 (ie about 10 years old) but I do have a Canon 350D (15 years old) that I could use if I needed to. It might be easier all round.

It would be great to have an update.

Regards

Steve.