Filter Stack

[barkis]

Since my RGB filters do not as far as I know, contain IR cut, is it reasonable to place an IR filter in the 2" nose piece of my filter wheel. This would of course, have the data being collected, passing through two filters some considerable distance apart, up to 3" possibly.

Would there be a chance of reflections, and/or image displacement, and I suppose, a requirement to re focus every filter change.

I could find the answers during use I know, but forewarned is forearmed as the saying goes.

Ron.

[daz]

This is what I do with my RGB set Ron. I recheck the focus after a change anyway.........

[barkis]

Thanks Daz.

[MartinB]

Ron, what scope are you using the filters with? It's worth doing a comparison with and without. There are advantages not using IR block especially if you aren't using a refractor. The IR can make a useful contribution to the image and an IR block filter does increase exposure times.

Are your RGB filters interference type ie reflect unwanted light or absorptive. Interference filters are more likely to cause internal reflections. You will know if you have a problem because you will have large halos appearing often off centre from the star causing the reflections

[barkis]

Martin, the intention was to image with refractors, either my ZS 66 or ED80 Scopes.

There will be the use of the 12" Meade too, with either the 6.3 or 3.3 Reducer depending on the targets.

As for the Filters, They are the just the LRGB ones I bought from Bern which he had on offer recently. I think the only way I can assess them will be after use, and note the results.

My camera is the MX916 Mono which has a medium size sensor I believe. I really should have had some imaging done by now, but The weather being so bad generally, but in particular up here I have never known such long periods of innaccessible skies. It's demoralising.

Right, Whinge over.

Ron.

A quote from Bern on the promotion of these filters.

1.25" LRGB filter sets which are the more expensive dichroic type

[MartinB]

Your filters are the interference type which reflect away unwanted light. They should have built in IR blocking and you would be best not using an additional IR block filter which could increase internal reflections especially with this type of filter. Bern will be able to confirm that they are IR blocking.

[barkis]

Your filters are the interference type which reflect away unwanted light. They should have built in IR blocking and you would be best not using an additional IR block filter which could increase internal reflections especially with this type of filter. Bern will be able to confirm that they are IR blocking.

Martin, I believe I did ask Bern about them incorporating IR Cut. He said yes in the case of the Lum. filter, but would need to find out about the others.

I will look at my messages just to confirm that I have that right.

Can't find the message Martin, but I am sure that's what Bern told me.

I'm sure all will be revealed in use though.

[moondog]

A quote from Bern on the promotion of these filters.

1.25" LRGB filter sets which are the more expensive dichroic type

Ron - the 'L' filter is an IR block filter. You don't need another IR block filter for the RGB ones.

MD

[barkis]

A quote from Bern on the promotion of these filters.

1.25" LRGB filter sets which are the more expensive dichroic type

Ron - the 'L' filter is an IR block filter. You don't need another IR block filter for the RGB ones.

MD

If you look back at the first reply to my post in this thread MD, Daz. said it is what he does. IE have the IR filter in the nose permanently, and move the RGB's into the light path when required.

Or, have I perhaps got him wrong.?

Cheers.

Ron.

[moondog]

Ron

Don't know about Daz but here's the situation with my Astronomik filters :-

These LRGB filters only cover the visible wavelengths - they specifically block both the UV and IR wavelengths.

In this case I can't see the point in having another IR blocking filter in front of the RG & B filters. You may need it with your set of filters, but I would be surprised.

8)

MD

[barkis]

I fully agree with you MD, but the reason I am querying mine, is I got them from Bern in a very special offer he had going. I snapped a set up, because the price was so good.

Not being clued up in the realm of filters, I asked Bernard if the filters incorporated IR Cut. He told be the Lum. did, but was not sure about the RGB ones. He was going to make enquiries for me, but he can't have the Info yet, as he has not got back to me.

All I am doing at the moment, is preparing my options should they not have IR Cut.

I hope they do, it would make thing simpler.

Anyway, I very much appreciate your input mate, thank you very much indeed. :salute:

Ron..

[Whippy]

Just thinking aloud, but would it matter if you had the Lum/IR cut filter on the nose piece of the camera if the RGB have IR cut or not? Because even if the the RGB filters have IR cut, they're only cutting the same frequencies (in theory) as the 'L' filter so should it make any difference to exposure times or image quality?

Tony..

[barkis]

That sounds a very plausible solution Tony. When exposing for Lum, I just need to have an empty Filter wheel port in the path.

I thank you sir.

[MartinB]

There will be some loss of light doubling up filters, there is also an increased risk of reflections and optical errors being introduced. There are advantages to not using IR block especially in mirror based optical systems. I think your plan of experimenting and seeing what works best makes a lot of sense Ron

[Whippy]

I'd be interested in how the experimentation comes out Ron as I'm looking at imaging with my Mak-Cass and I'm wondering if I'd need the IR cut on it. Of course I could try this out myself but......

Tony..

[barkis]

I'd be interested in how the experimentation comes out Ron as I'm looking at imaging with my Mak-Cass and I'm wondering if I'd need the IR cut on it. Of course I could try this out myself but......

Tony..

But?

[Whippy]

Oh I could make up some old rubbish Ron, but I can't be bothered! I'm sure i'll have a go at it at some point but I know the first sign of a clear ngiht, I'll be wanting to get on with it rather than experimenting. Besides, at f12, I'd have to have the camera running for about 3 days to get a half decent exposure!

Especially as looking at one of the more hysterical newspapers today, our Summer is to be washed out yet again, so looks like we'll have grab our chances when we can mate. I'm thinking a super fast astrograph could be the way forward .

Tony..

[barkis]

I know you are a big fan of Maks Tony, and you do harbour a yen for a particular size, 250?.

I thought you also had a fast Newt. but I'm probably thinking of somebody else.

I would like to think I could get the Meade up and running sooner rather than later, goodness knows I've had the damned thing long enough. I bought a EQ6 Pro. from Steve a while back, and that is still in it's box. All I've done in a practical way, is update the Firmware in the Handset.

I have so many jobs in hand at the minute, the priority being getting some wrought Iron railings put across the Patio to keep the dog from pearl diving in the Bl***y pond. It's taking longer than I hoped, simply coz my welding skills are non existent, and I keep having to grind blobs off where they shouldn't be Just a warm room to tag onto the back of the shed Obs. and I've been assured the Autumn months are all mine. Yeah, that'll be right.

Sorry mate, I'm gonna have to learn to condense my posts, I forget when to stop, Thing is, I don't talk this much.

Ron.

[Whippy]

I do have a C8N Ron, but it'll need the focuser upgrading before that goes anywhere near a camera! I dunno Ron, I'm still thinking of trimming the kit list down and just having one scope for imaging/visual and one for guiding/widefield... this time of year makes quite a few of us a bit doolally, I suppose we've got nothing else to do!

I've a simple solution for you though, get rid of the dog, then no gates needed and you're good to go for the obs .

Tony..

[barkis]

I do have a C8N Ron, but it'll need the focuser upgrading before that goes anywhere near a camera! I dunno Ron, I'm still thinking of trimming the kit list down and just having one scope for imaging/visual and one for guiding/widefield... this time of year makes quite a few of us a bit doolally, I suppose we've got nothing else to do!

I've a simple solution for you though, get rid of the dog, then no gates needed and you're good to go for the obs .

Tony..

Oh! man, I couldn't get shot of the JR. He's a mean little git, but I love him to bits, he's keeping me fit with all the walking we get through. At 10:30 pm every night, he drags his blanket out, telling me he wants to bed down. I put him in his basket, give him 3 dog chocs, put the kitchen light out, and he's asleep before I close the door. I kid you not, this is a ritual since he was 3 months old.