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Equipment Refractors Flattener
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Jerry Gerber avatar
Jerry Gerber avatar
Hello,

I recently purchased the Esprit 100  scope and the ASI2600mc camera.  I plan on using the flattener that comes with the telescope. 

The backfocus with the flattener to the sensor should be 63mm.   The camera's backfocus is 17.5mm.

I am guessing I'll require 45.5mm of spacers, is this correct?

I also have a .65 Apex focal reducer and have no idea how this will affect backfocus. 

This is a very challenging obsession!!!

Thanks!
Jerry
www.jerrygerber.com
Aygen avatar
Aygen avatar
Jerry,

Can you provide us a bit more information about your imaging train?

Your maths are correct. Usually, you would also need to consider the filter thickness (1/3 to add to the recommended backfocus). 

One side comment : ASI camera (among other brand) are known to have sensor tilt. My recommendation is to think about it too. If you don’t plan to have an FW or OAG and you have enough place left, consider also something like the GERD CTU to tackle potential tilt.

Aygen
Earle Waghorne avatar
Earle Waghorne avatar
Hi Jerry,

Check the flattener specification. I have and Esprit 80 and there is an 11 mm adapter attached to the flattener when it arrives and the backfocus from the adapter is 55 mm but 66 mm from the flattener.
Jerry Gerber avatar
Jerry Gerber avatar
Jerry Gerber:
Hello,

I recently purchased the Esprit 100  scope and the ASI2600mc camera.  I plan on using the flattener that comes with the telescope. 

The backfocus with the flattener to the sensor should be 63mm.   The camera's backfocus is 17.5mm.

I am guessing I'll require 45.5mm of spacers, is this correct?

I also have a .65 Apex focal reducer and have no idea how this will affect backfocus. 

This is a very challenging obsession!!!

Thanks!
Jerry
www.jerrygerber.com

I am going to be using the Esprit 100 with the ZWO ASI2600mc camera, the camera has a backfocus of 17.5mm.  I will also be using the flattener that comes with the scope and sometimes I will use the APEX .65 focal reducer as well as a 2x barlow (maybe).Where can I get all the necessary information to know exactly what spacers to get?   The scope, with the field flattener that comes with it, has a backfocus of 63mm. 

I'd like to avoid buying from Precision Parts (not sure if that's the exact name) as they are sorely overpriced.  

I guess another issue I just thought of is that the Starizona .65 reducer I bought is also a flattener.  Does this mean I should not use the flattener that came with the Esprit  100?    I'm a complete beginner but I love technical challenges and am studying everything I can to learn this stuff!

Thank you for help!
Jerry
andrea tasselli avatar
andrea tasselli avatar
Jerry Gerber:
I am going to be using the Esprit 100 with the ZWO ASI2600mc camera, the camera has a backfocus of 17.5mm. I will also be using the flattener that comes with the scope and sometimes I will use the APEX .65 focal reducer as well as a 2x barlow (maybe).Where can I get all the necessary information to know exactly what spacers to get? The scope, with the field flattener that comes with it, has a backfocus of 63mm.

I'd like to avoid buying from Precision Parts (not sure if that's the exact name) as they are sorely overpriced.

I guess another issue I just thought of is that the Starizona .65 reducer I bought is also a flattener. Does this mean I should not use the flattener that came with the Esprit 100? I'm a complete beginner but I love technical challenges and am studying everything I can to learn this stuff!

Thank you for help!
Jerry


If you are talking about this:

https://www.firstlightoptics.com/esprit-professional-refractors/skywatcher_flattener_esprit_100_20188.html

Then the backfocus is 55 mm from the rear threaded flange. You'd need a set of M48 adapter rings, commonly found on ebay and similar sites for few bucks. You might also need few spacers, again easily sourced from the above sites. Or the adapters you already have from the ASI2600 would suffice.

The starizona FR/FF won't need any field flattner ahead of it and the backfocus requirements are listed, for example, here:

https://www.365astronomy.com/starizona-apex-ed-s-0.65x-reducer-flattener-short-version?path=114_160_292

Be warned that the imaging circle is severely reduced and won't cover the ASI2600.
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