Narrow band

[bish]

Hi all,

I posted a while back about basic imaging when you have light pollution. It was suggested that NB would be a good idea. Do you need a special CCD camera to use NB filters? The ones that I have looked at all seem to say they are for CCD cameras. Does this mean that you can't use DSLR's for NB?

Thanks

[Davey-T]

You can get clip in NB filters for modded DSLRs.

Dave

[bish]

That was quick!  Thanks Dave.

[ollypenrice]

You can use NB filters with a DSLR but there's a problem; the colour filters of the Bayer Matrix on the DSLR remain in place unless you debayer them, which is a business!

Why does this matter? Well the Bayer Matrix gives pixels filtered red, green, green, blue. Of these, whatever an Ha filter does, only a quarter of the DSLR can see what's passing through. The red filters only let the Ha through so you are 25% efficient at best, assuming a modded DSLR.

Olly

[redmoo]

I am doing NB images with a modded DSLR at the moment. Using the 1.25 inch baader ones though (the clip in ones are really expensive). As is mentioned above, you will lose basically 3/4 of your resolution, depending on the filter that you are using, but I'm happy with the results so far. Now I just need some clear nights to get more data! 

One concern would be what scope (or rather which mount) you are using for doing the images? If you are using the 127 alt/az mak in your sig, you will have a really bad time with NB as the exposure lengths you need are a lot longer.

[bish]

Thanks Olly and redmoo. That explains things.

redmoo - I am only going to start with something fairly basic like a EQ5 (with motors) and SW 130P-DS

[Uranium235]

130pds? A wise choice sir

[bish]

130pds? A wise choice sir

Heard nothing but good - seen some of your pics too!

[redmoo]

Thanks Olly and redmoo. That explains things.

redmoo - I am only going to start with something fairly basic like a EQ5 (with motors) and SW 130P-DS

Are you going to be guiding? With the NB filters, you need approx 5 min exposures to get sensible amounts of data. If you are just going for the mount accuracy, at this exposure length you are going to be very susceptible to star trails etc. 

Also, if you buying new, I would really suggest going for the best mount you can get. 130pds does look like a nice scope though (thinking about one myself!)

[bish]

Are you going to be guiding? With the NB filters, you need approx 5 min exposures to get sensible amounts of data. If you are just going for the mount accuracy, at this exposure length you are going to be very susceptible to star trails etc. 

Also, if you buying new, I would really suggest going for the best mount you can get. 130pds does look like a nice scope though (thinking about one myself!)

Sounds like things could get more expensive than I thought then. I don't know about imaging but guess it would be hard to get 5 min exposures out of an EQ5?  It might be sensible to start with a fairly cheap set up, EQ5 + 130P-DS , 1100D and a CLS clip filter and see how I get on.  I can always upgrade the mount and go down the NB route later.

[bish]

You can use NB filters with a DSLR but there's a problem; the colour filters of the Bayer Matrix on the DSLR remain in place unless you debayer them, which is a business!

Why does this matter? Well the Bayer Matrix gives pixels filtered red, green, green, blue. Of these, whatever an Ha filter does, only a quarter of the DSLR can see what's passing through. The red filters only let the Ha through so you are 25% efficient at best, assuming a modded DSLR.

Olly

Forgot to say well done on your excellent image in this months AN.

[ollypenrice]

Forgot to say well done on your excellent image in this months AN.

Thanks. I haven't seen it! Which one is it?

Are you going to be guiding? With the NB filters, you need approx 5 min exposures to get sensible amounts of data. If you are just going for the mount accuracy, at this exposure length you are going to be very susceptible to star trails etc. 

Also, if you buying new, I would really suggest going for the best mount you can get. 130pds does look like a nice scope though (thinking about one myself!)

Good point. Personally my Ha subs are almost always 30 minutes.

Olly

[redmoo]

Thanks. I haven't seen it! Which one is it?

Good point. Personally my Ha subs are almost always 30 minutes.

Olly

30 mins? wow, never even thought of going for that much. Then again, I guess it is target dependent. I am only just beginning, so going for pretty bright 'easy' to image targets.

Sounds like things could get more expensive than I thought then. I don't know about imaging but guess it would be hard to get 5 min exposures out of an EQ5?  It might be sensible to start with a fairly cheap set up, EQ5 + 130P-DS , 1100D and a CLS clip filter and see how I get on.  I can always upgrade the mount and go down the NB route later.

With this game, things are always more expensive. I started in November last year with a 250 pound 127 MAK scope. Soon realised that this did not meet what I wanted it to do, and upgraded to a HEQ5 pro and a 200p. Add in a guide cam, guide scope (st80), full set of NB filters and there are still more bits to buy. 

One thing to look at might be second hand equip. I managed to get a scope and mount for 500 pound. Guide scope was 80 pound, Guide cam I salvaged from work. 

The NB filters were expensive (280 pound from FLO) but it makes a lot more sense to buy the full set than to buy them one at a time. 

If I could start all over again, I would probably go for a second hand HEQ pro with synscan, a new 130pds and some combination of guide cam/scope. Then a decent CLS CCD clip in filter from astronomik and a modded DSLR. 

There are some really good threads on getting started with imaging and imaging on a budget, but most of them will suggest spending the most you can on the mount, as this is the part that will not only dictate how good your images are, but give you plenty of scope (excuse the pun) to upgrade in the future.

[bish]

Thanks. I haven't seen it! Which one is it?

Good point. Personally my Ha subs are almost always 30 minutes.

Olly

It's the flame and HH (on p.26)

[bish]

30 mins? wow, never even thought of going for that much. Then again, I guess it is target dependent. I am only just beginning, so going for pretty bright 'easy' to image targets.

With this game, things are always more expensive. I started in November last year with a 250 pound 127 MAK scope. Soon realised that this did not meet what I wanted it to do, and upgraded to a HEQ5 pro and a 200p. Add in a guide cam, guide scope (st80), full set of NB filters and there are still more bits to buy. 

One thing to look at might be second hand equip. I managed to get a scope and mount for 500 pound. Guide scope was 80 pound, Guide cam I salvaged from work. 

The NB filters were expensive (280 pound from FLO) but it makes a lot more sense to buy the full set than to buy them one at a time. 

If I could start all over again, I would probably go for a second hand HEQ pro with synscan, a new 130pds and some combination of guide cam/scope. Then a decent CLS CCD clip in filter from astronomik and a modded DSLR. 

There are some really good threads on getting started with imaging and imaging on a budget, but most of them will suggest spending the most you can on the mount, as this is the part that will not only dictate how good your images are, but give you plenty of scope (excuse the pun) to upgrade in the future.

I am already starting to see what a slippery slope it can be. Wait a bit and look at the second hand stuff is probably the most sensible (ie don't use the credit card) option. It's bad enough having aperture fever with the dob!

[lensman57]

Hi all,

I posted a while back about basic imaging when you have light pollution. It was suggested that NB would be a good idea. Do you need a special CCD camera to use NB filters? The ones that I have looked at all seem to say they are for CCD cameras. Does this mean that you can't use DSLR's for NB?

Thanks

NB filters and un modded DSR are bad news, less of a bas news with a modded DSLR but still not ideal. If you want to do NB imaging properly then you need a Mono CCD. If you want to beat LP so long as the LP level is moderate and there is no Mr Moon about then a good LP filter or an Astronomik CLS CCD clip filter would help but there is no substitute for dark skies and those are like hens teeth.

A.G

[bish]

NB filters and un modded DSR are bad news, less of a bas news with a modded DSLR but still not ideal. If you want to do NB imaging properly then you need a Mono CCD. If you want to beat LP so long as the LP level is moderate and there is no Mr Moon about then a good LP filter or an Astronomik CLS CCD clip filter would help but there is no substitute for dark skies and those are like hens teeth.

A.G

Thanks AG. I think I will go down the road of a CLS clip. My parents live in a fairly dark area which probably worth the hours drive too.

[lensman57]

Thanks AG. I think I will go down the road of a CLS clip. My parents live in a fairly dark area which probably worth the hours drive too.

That is the best option. Joking aside once you get used to using the DSLR for DSO imaging you could have a crack at using an Astronomik Ha clip filter with the DSLR but as Olly said you loose 3 out of the 4 pixels and the processing stages are a bit of a pain but it is doable.

A.G

[Astrosurf]

This is a widfield Ha pic I took with a DIY Ha filter a friend made. He stuck a standard 1.25" filter into a collar of thinish rubber. It stayed in only if I used a lens, not prime focus! So this was done with my modded 600D with a 200mm lens on an Astrotrac. But it shows what can be achieved. It's a bit noisy due to the Bayer matrix issue, I guess.

Alexxx