Go Back   IceInSpace > Equipment > Eyepieces, Barlows and Filters

Reply
 
Thread Tools Rate Thread
  #1  
Old 17-08-2020, 12:19 PM
Stonius's Avatar
Stonius (Markus)
Registered User

Stonius is offline
 
Join Date: Mar 2015
Location: Melbourne
Posts: 1,495
Do you need to remove sensor window to shoot UV?

I was thinking of getting a Bader Venus filter to play with, but I know that sensor windows sometimes have UV blocking built in.



I'm using an ASI 290 Mono, and as far as I can see, the response at those wavelengths (350nm) is only around 25% of it's maximum sensitivity, which seems to peak more in the red.


Is this just a natural effect of the sensor or is the sensor window coated to reject these wavelengths?


I guess Venus is a pretty bright target (!) but still...



Cheers


Markus
Reply With Quote
  #2  
Old 17-08-2020, 12:33 PM
sunslayr (David)
Registered User

sunslayr is offline
 
Join Date: Nov 2018
Location: Perth
Posts: 209
That would match up with the chart on this page for the ar window. I'd say you would need to remove it for 350nm and below.
Reply With Quote
  #3  
Old 17-08-2020, 01:00 PM
Stonius's Avatar
Stonius (Markus)
Registered User

Stonius is offline
 
Join Date: Mar 2015
Location: Melbourne
Posts: 1,495
Quote:
Originally Posted by sunslayr View Post
That would match up with the chart on this page for the ar window. I'd say you would need to remove it for 350nm and below.

Hmm, might make more sense to try and capture it with my 1600 then. No need for modifications!
Reply With Quote
  #4  
Old 17-08-2020, 03:08 PM
Merlin66's Avatar
Merlin66 (Ken)
Registered User

Merlin66 is offline
 
Join Date: Oct 2005
Location: Junortoun Vic
Posts: 8,904
I use an ATIK 314L, ASI 1600MM and ASI 174MM for spectroscopy the QE curves just give some signal down around 370nm, below that the atmospheric transmission starts to kick in - the combo work against imaging in the far UV.
Most objectives (and obviously mirrors) will allow some imaging in the UV.
This spectrum of Sirius was taken with the Genesis and ATiK 314.
Attached Thumbnails
Click for full-size image (sirius_blue.jpg)
48.8 KB10 views
Reply With Quote
  #5  
Old 17-08-2020, 03:34 PM
Stonius's Avatar
Stonius (Markus)
Registered User

Stonius is offline
 
Join Date: Mar 2015
Location: Melbourne
Posts: 1,495
Quote:
Originally Posted by Merlin66 View Post
I use an ATIK 314L, ASI 1600MM and ASI 174MM for spectroscopy the QE curves just give some signal down around 370nm, below that the atmospheric transmission starts to kick in - the combo work against imaging in the far UV.
Most objectives (and obviously mirrors) will allow some imaging in the UV.
This spectrum of Sirius was taken with the Genesis and ATiK 314.

So you're saying even without the sensor window cutting the UV the CMOS sensitivity just drops off regardless?


Looking at the graph for the 1600MM, it would still only get me to around 30% of peak efficiency, so that would make sense.


I don't know much about spectroscopy so I'm not sure how to read the image you posted. The bottom scale is tenths of a nM/? It looks like the amplitude drops off as the wavelengths get shorter, but I don't know enough to guess if this is attenuation from the imaging train, or just black body radiation curves?


Cheers


Markus
Reply With Quote
  #6  
Old 17-08-2020, 03:44 PM
Merlin66's Avatar
Merlin66 (Ken)
Registered User

Merlin66 is offline
 
Join Date: Oct 2005
Location: Junortoun Vic
Posts: 8,904
Markus,
On the spectral graph the X axis is in wavelength Angstrom.
Sirius is a A type star with prominent H Balmer series absorption lines - that's what you see. The curve (intensity values) drop off towards the left partly due the spectrum of Sirius (Back body) but also the camera sensitivity.
The ability to record much below 3700A is compromised.
Reply With Quote
  #7  
Old 17-08-2020, 05:50 PM
Stonius's Avatar
Stonius (Markus)
Registered User

Stonius is offline
 
Join Date: Mar 2015
Location: Melbourne
Posts: 1,495
Quote:
Originally Posted by Merlin66 View Post
Markus,
On the spectral graph the X axis is in wavelength Angstrom.
Sirius is a A type star with prominent H Balmer series absorption lines - that's what you see. The curve (intensity values) drop off towards the left partly due the spectrum of Sirius (Back body) but also the camera sensitivity.
The ability to record much below 3700A is compromised.



Ah, interesting - thank you for explaining :-)


Markus
Reply With Quote
  #8  
Old 17-08-2020, 10:12 PM
JA
.....

JA is offline
 
Join Date: Oct 2016
Location: Melbourne, Australia
Posts: 2,945
Quote:
Originally Posted by Stonius View Post
I was thinking of getting a Bader Venus filter to play with, but I know that sensor windows sometimes have UV blocking built in.
Hi M,

Not only will the sensor design and any coverglass potentially limit performance in to the UV, but the scope or lens will also limit UV performance
below about 350nm. There are some optics that can reach down to about 300nm and some very expensive specialist UV lenses that approach 200nm.

Best
JA
Reply With Quote
  #9  
Old 17-08-2020, 10:33 PM
Stonius's Avatar
Stonius (Markus)
Registered User

Stonius is offline
 
Join Date: Mar 2015
Location: Melbourne
Posts: 1,495
So ...I understand that the response is attenuated in that part of the spectrum.


Yet Venus is bright.


The question is 'will the response be so attenuated as to make it a foolish quest with current equipment?'.


Best,


Markus
Reply With Quote
Reply

Bookmarks

Thread Tools
Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +10. The time is now 05:54 PM.

Powered by vBulletin Version 3.8.7 | Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Advertisement
Bintel
Advertisement
Testar
Advertisement