My last Saturns, IR and no IR comparison

[iceman (Mike)]

Hey guys.

For the first time in about 6 weeks I was able to do some dob-based imaging on Saturday night.

Now that daylight savings has gone and it's darker earlier, Saturn is visible again for a short time before it goes behind a tree in the north-west.

So I gave it one last shot for the year, and decided to try and do an IR-filter vs no-IR-filter comparison.

Unfortunately the seeing was only average and so the images aren't that great, probably on par with the rest of my so-so saturn images this year.

For the IR filter vs no IR filter images, I used the same settings, or as same as I could get them. They had to be refocussed slightly and it seems that the IR filter cuts out a bit of light as I had to use slightly less gain when I took the IR filter out.

They were processed almost identically, that is, best as I could make them look in registax.

The top row of images are processed in registax/PS, and the bottom row are the same images as their vertical counterpart but processing was done in registax and astraimage.

1/25s shutter
Low gain
Saturation full
Gamma 0

What to deduce from my expirement? Not much tbh.. perhaps the no IR filter image is slightly more washed out and not as many fine details visible..? But with the average seeing and resulting average images, it's hard to draw much in the way of a conclusion.

More experiments are needed, on nights of better seeing, and from people with tracking scopes

[Striker (Tony)]

Nice one Mike.....we need more of this as far as comparisons go.......us noobs what to know what the difference's are using differnet filters and methods as you have shown us with the above pics....

Its ok to see great pics using a particular method but it makes it much more informative when their is a comparison of the same image.

I am still waiting for someone do post comparitive pics using focal reducers and Barlows so we can see the benifits of either.

[ving (David)]

good one. seems without is alot crisper

I believe the IR filter is only an issue with refractors. Due to the different refractive index of IR. It is apparently quite complicated, but it is to do with differening wavelengths of IR when going through glass, even very well corrected glass as in APO's. Others far more versed in this matter could probably explain much better.

Peter

[Howzat (Phil)]

Nice Mike. I might have to give imaging a go What IR filter do you use?

Now that daylight savings has gone and it's darker earlier, Saturn is visible again for a short time before it goes behind a tree in the north-west.

I'm not gunna touch that one

[iceman (Mike)]

It's an edmund-scientific one, I got it from Telescopes & Astronomy in SA.

[Howzat (Phil)]

Ahh that's right. You sent back the cheaper one you got with your toucam.