M48 T ring adaptor width

[smoggy]

I'm currently putting my shopping list together to see if astrophotography is for me.  However, the cheapest part has got me stumped.  I've been advised to buy the stellamira 0.8x field flattener/reducer for my scope which requires 55mm of back focus.  I believe the distance to the sensor in my camera if 44mm which leaves the M48 T ring adaptor needing to be 11mm.  Is 11mm a standard width as I'm struggling to find any website that quotes the thickness of these adopters unless it is ultra thin.  

[Davey-T]

Yes it's a standard thickness designed for DLSRs.

Dave

[smoggy]

Thank you very much!

[Robindonne]

Oke while being also starting i came across this one.  The ring is 1,5 mm so it leaves even room for a 9 mm oag in the whole setup.  I was struggling a bit with all these accesoires and oag-configurations, but got a lot of help here!   Only thing is the es mpcc from the added picture is only a flattener and no reducer.  Don’t  know if the combined one is also available but this one came for sale by a person who bought the wrong flattener.

 

ps.  While owning the mpcc and knowing the rare 1,5 mm thickness of the t-ring I recognized the ring on the covid-app.  It looks like it has the same thickness.  So worth a try.  I ordered one to find out

Edited June 7, 2020 by Robindonne

[alacant]

9 hours ago, smoggy said:

M48 T ring adaptor needing to be 11mm

Hi

The standard adapters are 9mm, 10mm or 11mm depending upon the make of the camera.

You don't say which camera, but all will adjust backfocus of a dslr to around 55mm. e.g. this one  (assume Canon as you state 44mm)

Cheers and HTH

[Alien 13]

I actually use a M42 to EOS chipped adapter which is about 1.2mm thick in conjunction with a 10mm T extension tube to give a total of 44.2mm which is perfect for my WO FR/FF spacing requirements. Now this shouldnt work as the M42 and T have differing thread pitches but mine screw together fine and are never taken apart, the big benefit of the M42 adapter is it is a much tighter fit to the camera body.

Alan

[SimM]

16 hours ago, smoggy said:

I'm currently putting my shopping list together to see if astrophotography is for me.  However, the cheapest part has got me stumped.  I've been advised to buy the Stellamira 0.8x field flattener/reducer for my scope which requires 55mm of back focus.   

With your flattener/reducer you simply want the “wide” T-Mount for your camera with M48.

Canon, Nikon and others, have a flange to sensor distance that varies slightly but is around 44mm. When you attach an accessory they will specify a standard depth of 55mm.

The job of the T-Mount is to attach the camera bayonet fitting to your accessory and provide the correct spacing of 55mm. 44mm accommodates the mirror flip up of a DSLR. Many T-Mounts, if not specified, are M42.

T-Mounts can be also found for M48 or “wide” versions. Astronomy cameras have no need for the mirror box e.g. ZWO are often only 17.5mm. They usually are packaged with extension rings T-Adapters to maintain the 55mm standard and make them compatible.

Without one/both of their adapters, filter wheels or OAGs can be included within the back focus required. I found the different sizes and names used a little confusing. This web link explains the different sizes:

https://agenaastro.com/articles/guides/miscellaneous/astronomy-threads-explained.html

M42 and M48 have differing internal diameters and the bigger size is less likely to vignette an image. M48 is also the thread size of 2” filters!

Simon

Edited June 8, 2020 by SimM
Misquoted the wrong info for OP.

[alacant]

1 hour ago, SimM said:

you simply want the “standard” T-Mount for your camera with M42

Hi

But  the OP will then need another adapter:(

Perhaps best to keep it simple and go the direct route with the m48...

Cheers