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Do you .... blink ??

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Bikeman's picture
Bikeman
User offline. Last seen 43 weeks 4 days ago. Offline
Joined: 07/21/2009
Posts: 289
Teams: DSLR Documentation and Reduction, Mira Fourier Coefficient Team, VStar Software Development
Posted: October 10, 2009 - 9:41am

Hi all!

I was wondering ... on each observation night, we all are producing several stacked images with identical exposure parameters of the same (wide) field of stars, with a total exposure time per image of perhaps 60+ seconds. I looked at one of my stacks and compared it to a star map, and found I could identify individual stars down to about 8.8 mag with some confidence. I guess it will be similar for other DSLR photometrists.
So the obvious question is whether one should bother to invest a little extra time after doing the quantitative photemetry part to check (e.g. by blinking the stacked image with a reference shot) whether there's something that didn't appear there before.

OTOH, 8.8 mag is not THAT impressive as a detection threshold....so what about you: Do you even bother to blink?

CS
Heinz

P.S.: To give an impression: this is a screenshot of displaying one of my stacked Eps Aur images in AIP4win  at 1:1 resolution and with display settings favorable for "blinking". Eps Aur is the bigger disk at the left and eta and zeta Aur are at the right hand side. The "stripy" artefacts are introduced during stacking by automatically slightly rotating images to compensate for field rotation (as just a static tripod is used).

 

 

Des Loughney's picture
Des Loughney
User offline. Last seen 35 weeks 4 days ago. Offline
Joined: 08/29/2009
Posts: 37
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Posted: October 10, 2009 - 1:48pm

Heinz,I don't know about ' blinking' but there may be quite a lot of variable stars within a field of view.The field of view of a Canon 450D and an 85 mm lens is quite large, With the setting of ISO 800, f 2.8 and an exposure of 5 seconds one can study variables ( obtaining a reasonable signal to noise ratio ) between 6.5 and 8. With a 200 mm lens you can go down to magnitude 9. When you are studying the magnitude range of 6.5 to 8 it is sometimes interesting to consider how many other variables are in the field of view apart from the target star and comparators. A planetarium programme such as Starrynight Pro can sometimes reveal quite a number which are worth monitoring.I have sometimes wondered about doing some experiments using the above settings with an 85 mm lens. I would take 30 images and then process them with sum stacking rather than average stacking and study what is revealed.Des

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