Grab and go scope for Night Vision

[GavStar]

I still think refractors give a crispness of view with night vision that reflectors can’t match 😀

Also I believe that mirrors have some light transmission loss that refractors don’t have. The two mirrors in an imaging Newtonian f4 can lead to a light transmission loss of 80 percent meaning it’s actually operating at f5ish rather than f4...

[Deadlake]

You forgot to mention collimation and acclimation. 😀😀😀 Actual quite scary number of threads on CN around collimation.... put me off RC types...

[PeterW]

Depends on the mirro coating, can go >95%, easier to get bigger and faster... lots of options.

Peter

[Deadlake]

9 hours ago, PeterW said:

Depends on the mirro coating, can go >95%, easier to get bigger and faster... lots of options.

Peter

How does age affect a mirror’s coating?

[GavStar]

10 hours ago, PeterW said:

Depends on the mirro coating, can go >95%, easier to get bigger and faster... lots of options.

Peter

Eddgie on CN estimates his Boren Simon has transmission in the order of 85% which is the figure Celestron gives for its latest coated scts.

[Deadlake]

8 minutes ago, GavStar said:

Eddgie on CN estimates his Boren Simon has transmission in the order of 85% which is the figure Celestron gives for its latest coated scts.

Googling for mirror transmission for reflectors comes up with limited hits, for instance I wondered if an Epsilon would have a higher transmission. 

NV I believe is not so sensitive to the green/blue frequency bands, do we have transmission values for the red band that NV is sensitive too?
 

[GavStar]

4 minutes ago, Deadlake said:

Googling for mirror transmission for reflectors comes up with limited hits, for instance I wondered if an Epsilon would have a higher transmission. 

NV I believe is not so sensitive to the green/blue frequency bands, do we have transmission values for the red band that NV is sensitive too?
 

The figure I quoted for Celestron is at the 656 halpha band that is critical for nv nebulae observing. I haven’t seen anything specific regarding the Epsilon transmission but would think it would be similar to the other scopes.

As Peter says the key advantage of reflectors is the ability to have large aperture to get the necessary image scale for smaller objects with nv, which is what I use my c11 edge and 16 inch dob for.

[Deadlake]

3 minutes ago, GavStar said:

The figure I quoted for Celestron is at the 656 halpha band that is critical for nv nebulae observing. I haven’t seen anything specific regarding the Epsilon transmission but would think it would be similar to the other scopes.

As Peter says the key advantage of reflectors is the ability to have large aperture to get the necessary image scale for smaller objects with nv, which is what I use my c11 edge and 16 inch dob for.

What about 700 nm range (red)? 

Agree for larger aperture SCT looks the way to go, EdgeHD series looks like less maintenance than other mirror based systems. At lot of RC scopes have quartz mirrors which aids with cool down, but for  NV less sensitive to acclimation.

[GavStar]

17 minutes ago, Deadlake said:

What about 700 nm range (red)? 

Agree for larger aperture SCT looks the way to go, EdgeHD series looks like less maintenance than other mirror based systems. At lot of RC scopes have quartz mirrors which aids with cool down, but for  NV less sensitive to acclimation.

Diagram direct from celestron document 

 

 

Edited November 25, 2020 by GavStar

[PeterW]

Depends on the coating material and whether it’s been AR coated, like celestron, Orion and others can add to improve the result. If you treat coating a with care then they should last for ages, they are typically oxide overcoated that stops them being corroded.  Reflectors typically have fewer, but lossier interfaces compared to refractors. 656nm is close enough to visible that broadband coati NV a should still work fine. Aluminium coating S have a bit of a drop around 800, so maybe we should ask for protected silver mirrors instead? https://www.edmundoptics.co.uk/knowledge-center/application-notes/optics/metallic-mirror-coatings/
No info on them different “coated mirrors” that companies have, which could reduce this somewhat.

Peter

[Deadlake]

This could be a new interesting scope for NV. 

https://www.facebook.com/permalink.php?id=103346594423278&story_fbid=318484316242837

near to relaese, but is 260 mm, Flat field,  f5 and had reported 95% transmission .

However I'd wait for a field test before I went any further.

Planewave make one similar to this but 3x the cost.