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Old 12-11-2021, 06:52 PM
Stephane
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Location: Melbourne, Australia
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What T-adapter do I need?

Hi all,

Apologies for my beginner questions, I am setting up my first rig. I have a Nikon camera and have a T-ring which connects fine to the DSLR. I have ordered a Newtonian OTA (Bintel BT200 f/5) which is coming in a few days. I have also ordered a 2-inch Optolong L-Extreme filter. My EQ6-R pro arrived today. Guide cam is acquired and guide scope is on its way.

I am still missing a T-adapter and am not sure what I need to buy. Where is the L-Extreme filter placed? Between the T-Ring and T-adapter? Or between the T-adapter and OTA? Will I even need a t-adapter if I get a coma corrector? Also, most t-adapters are 1.25 inch, so will that work with a 2-inch filter? I am so confused, so any help will be much appreciated. I hope I am making sense...

Many thanks,
Stéphane
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Old 12-11-2021, 07:19 PM
JA
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Hi Stephane,

What you need depends a little on what you've got.

If you have a 2 inch focuser (I'm reasonably certain that your Bintel 200 f/5 would, but it pays to check). It says it has a 2inch to 1.25inch adapter so it's very likely unless your scope is modified somehow. OK so let's go with a 2 inch focuser (that's its internal diameter).

Your Nikon: is it full frame, APSc or other sensor size? This is important to know as for full frame you need as large an internal adapter diameter as possible otherwise you will vignettte (cut off) the light to the ~43.3mm diagonal of the sensor by using the M42 type T-ring. On full frame you want a "large" t-ring type thread, ususally it's M48. So it would be important to also know about the t-ring you already purchased is it an M42 or M48 thread? It may say so on the t-ring itself. By knowing this you can then order the right telescope adpater tube to the camera, which is essentially a 2 inch outside diameter tube at one end and an M42 or M48 male thread at the t-ring (camera end) of the tube. This in turn screws in to the t-ring female thread (mounted on the camera).

Usually (sometimes?) the INSIDE of the telescope end of this tube also has an M48 female thread in to which you can screw your 2 inch (M48) filters.

If you purchased the scope from Bintel I'm sure they could hook you up with the right stuff.

Best
JA

Last edited by JA; 12-11-2021 at 08:05 PM.
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  #3  
Old 12-11-2021, 08:30 PM
Stephane
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Quote:
Originally Posted by JA View Post
Hi Stephane,

What you need depends a little on what you've got.

If you have a 2 inch focuser (I'm reasonably certain that your Bintel 200 f/5 would, but it pays to check). It says it has a 2inch to 1.25inch adapter so it's very likely unless your scope is modified somehow. OK so let's go with a 2 inch focuser (that's its internal diameter).

Your Nikon: is it full frame, APSc or other sensor size? This is important to know as for full frame you need as large an internal adapter diameter as possible otherwise you will vignettte (cut off) the light to the ~43.3mm diagonal of the sensor by using the M42 type T-ring. On full frame you want a "large" t-ring type thread, ususally it's M48. So it would be important to also know about the t-ring you already purchased is it an M42 or M48 thread? It may say so on the t-ring itself. By knowing this you can then order the right telescope adpater tube to the camera, which is essentially a 2 inch outside diameter tube at one end and an M42 or M48 male thread at the t-ring (camera end) of the tube. This in turn screws in to the t-ring female thread (mounted on the camera).

Usually (sometimes?) the INSIDE of the telescope end of this tube also has an M48 female thread in to which you can screw your 2 inch (M48) filters.

If you purchased the scope from Bintel I'm sure they could hook you up with the right stuff.

Best
JA
JA, thank you for your reply. My Nikon D7000 has an APS-C sized sensor. Thus, I am assuming an M42 thread will work without vignetting? I forgot to mention that the Bintel OTA is a second hand “never used” piece that I bought off gumtree. I did this because Bintel is out of stock, and will be for months to come. All original accessories are included so the 2” to 1.25” adapter should be there… From photos I’ve seen, it does look like there is a two inch female thread on the OTA, but might check with Martin.

If I understand what you are saying, I should avoid the 1.25” T-Adapter, and rather get a 2” one (M42 being sufficient).

Also, would a coma corrector such as the Baader MPCC MkIII “replace” the T-Adapter?

Many thanks,
Stéphane
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  #4  
Old 12-11-2021, 09:59 PM
Startrek (Martin)
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Bintel 8” f5 has 2” focuser
Set up is as follows
Nikon camera > Nikon T ring adapter > Baader Mk3 coma corrector > 2” Optolong L Extreme screws into end of coma corrector , then into focuser
From Nikon camera sensor to coma corrector should be around 55mm to achieve focus and eliminate coma
I have a Canon so I didn’t need any additional spacers to achieve focus and eliminate coma but when I use my ZWO2600MC cooled OSC , I needed an additional 2mm spacer to eliminate coma ( sensor to coma corrector ended up 57mm )
You will have to test your new set up and you may or may not need additional spacers or screwed rings ( available from Bintel )

Hope the above helps
Martin
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  #5  
Old 12-11-2021, 10:16 PM
Stephane
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Join Date: Sep 2021
Location: Melbourne, Australia
Posts: 517
Quote:
Originally Posted by Startrek View Post
Bintel 8” f5 has 2” focuser
Set up is as follows
Nikon camera > Nikon T ring adapter > Baader Mk3 coma corrector > 2” Optolong L Extreme screws into end of coma corrector , then into focuser
From Nikon camera sensor to coma corrector should be around 55mm to achieve focus and eliminate coma
I have a Canon so I didn’t need any additional spacers to achieve focus and eliminate coma but when I use my ZWO2600MC cooled OSC , I needed an additional 2mm spacer to eliminate coma ( sensor to coma corrector ended up 57mm )
You will have to test your new set up and you may or may not need additional spacers or screwed rings ( available from Bintel )

Hope the above helps
Martin
Thanks Martin, that answers all my questions. I am glad the coma corrector can replace the T2 adapter. Once I receive the OTA (in the next few days) and pending good whether, I’ll experiment to see if spacers are needed.

Many thanks,
Stéphane
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