HM Adjustable Slit

[theodog (Jeff)]

Hi All,
I am still waiting for Surplus Shed to get these in stock. So, as for my impatience, I decided to make one.
On another forum, it was suggested an improvement to the SA100 mask would be a full slit (12mm)that could be narrowed onto the star image after it is identified in the field. This is my attempt to do this. It will fit into a 1 1/4" and recieve 1 1/4" nose-pieces with the SA100 attached and sitting just behind the slit. The slit can be adjusted for width and for position in the field. It should also be able to align with the grating on the SA.
While doing this I thought that a slit behind the SA that only allows the spectrum to reach the CCD might be better.
Any ideas?
Cheers Jeff

[Terry B]

Where is the focus point?
If the SA is places well in front of the focus then the slit will just block most of the spectrum rather than what you want to achieve.
I tried a single sided mask like a one sided slit placed in front of the SA and this worked to get rid of most of the background stars that contaminated the spectrum but it made it very difficult to focus the spectrum so I removed it.
Do you need some sort of lens in the optical train to make this work?

[theodog (Jeff)]

Originally Posted by Terry B

Where is the focus point?

The focus point is still the CCD. I am really trying to achieve an adjustable mask. Still I think guiding will be impossible with no light falling on the guiding chip.

Originally Posted by Terry B

If the SA is places well in front of the focus then the slit will just block most of the spectrum rather than what you want to achieve.

With more thought, I agree.

Originally Posted by Terry B

I tried a single sided mask like a one sided slit placed in front of the SA and this worked to get rid of most of the background stars that contaminated the spectrum but it made it very difficult to focus the spectrum so I removed it.

I used this to do a spec. of Canopus. With the slit wide open, focus was as normal. I then closed the slit to mask as much as I could, while still allowing the spectrum through. Similar to the circular mask.

Originally Posted by Terry B

Do you need some sort of lens in the optical train to make this work?

With this slit pionted towards a light inside and no optics in the train I imaged below.

[Terry B]

This makes sense. Very good.
My mask was just alfoil so it wasn't adjustable. I like the idea of the adjustable mask but I think it would be better infront of the SA.