changing the airgap to correct for blue light, questionable results.

[Kitsunegari]

There is some speculation over at cloudynights that increasing the airgap of your objective lens can increase corrective imaging of violet light which is usually never  corrected  on any telescope. 

https://www.cloudynights.com/topic/770832-a-volks-scope-analysis/

I tried this on my explore scientific firstlight 127x1200 and find the results to be almost identical.  

The oem airgap is .1mm as shipped from ES.

I will check collimation and do a second test, because i forgot to do this on this test.    Every time the objective comes off you must recollimate because the screw holes dont always line up exactly.

There is a 4 minute difference between these two images.

OEM airgap.  (7 frames)

 

 

2mm airgap (9 frames)

Edited June 13, 2021 by Kitsunegari

[Victor Boesen]

Not sure about others, but to me it seems like the 2mm spacing looks sharper  Especially around the sunspot and on the bright part of the disk.

[Kitsunegari]

16 minutes ago, Victor Boesen said:

Not sure about others, but to me it seems like the 2mm spacing looks sharper  Especially around the sunspot and on the bright part of the disk.

It may need collimation,  i forgot to check it on the oem setting because i had taken the objective off to clean it.     I didnt mark the screw holes so it was rotated away from its original position.

I do agree it looks sharper but i collimated the second one

 

I am recollimating right now on the .1mm for a second test.       Also i have recorded the floater prom with a longer timelapse using both settings to make sure it wasnt just a seeing issue.

[Kitsunegari]

Okay, here is a 37 frame test on the same optics ;  without checking collimation on the .1mm gap.  

 

I see no difference between the two.  IDentical processing, identical exposure settings.

OEM .1mm airgap

 

2mm airgaip.

 

Edited June 13, 2021 by Kitsunegari

[Victor Boesen]

Yup, that definitely looks the same to me as well

[Kitsunegari]

Brought the attention of this over to astrobin forum and got some interesting replies.  

 

https://www.astrobin.com/forum/c/astrophotography/equipment/increasing-the-airgap-on-a-refractor-to-increase-correction-for-violetblue-light/?page=1#post-39052

 

(Thanks HbAstro)

 

OEM

 

1.7mm airgap

 

2.35mm airgap.