Which filters for imaging nebulas with a SW 200PDS?

[kaymado]

Hello fellow sky gazers,

Joining this forum has really improved my little knowledge over this somehow complex topic, but i would like to have some expert advice before going on to buy more expensive parts to increase my imaging quality.

I know I cannot expect much from an eq5 (dual axis motor driven) mount which is what i have at the moment, but the question this time is about filters. The mount will be upgraded next year.

Using a mod'd Canon 450D and so far I've only bought the baader S-UHC (nebula) filter which is from what I understand, meant for slightly light polluted skies. (Edinburgh is really not that bad actually)

However, I've been thinking of getting an Ha and Oiii filter and would like to know your thoughts on this setup.
Are they suitable for a newtonian reflector? and does the fact that I have full spectrum camera help? (i mean, is the benefit clearly visible?)

Can I combine the S-UHC with Ha and Oiii filters?

I'm thinking of buying the Ha 7nm first. Is this the right decision?

I've not got the comma corrector yet, should that come first?

Thanks to all in advance.

Kay

[Oily]

Can't answer your filter question but I think you underestimate your mounts capablities Kay,have a look here to give you an idea on what's achieveable with your EQ5/200PDS

http://astrocasto.blogspot.co.uk/

[lensman57]

Hello fellow sky gazers,

Joining this forum has really improved my little knowledge over this somehow complex topic, but i would like to have some expert advice before going on to buy more expensive parts to increase my imaging quality.

I know I cannot expect much from an eq5 (dual axis motor driven) mount which is what i have at the moment, but the question this time is about filters. The mount will be upgraded next year.

Using a mod'd Canon 450D and so far I've only bought the baader S-UHC (nebula) filter which is from what I understand, meant for slightly light polluted skies. (Edinburgh is really not that bad actually)

However, I've been thinking of getting an Ha and Oiii filter and would like to know your thoughts on this setup.

Are they suitable for a newtonian reflector? and does the fact that I have full spectrum camera help? (i mean, is the benefit clearly visible?)

Can I combine the S-UHC with Ha and Oiii filters?

I'm thinking of buying the Ha 7nm first. Is this the right decision?

I've not got the comma corrector yet, should that come first?

Thanks to all in advance.

Kay

There is no need to combine Ha and UHC or any other filter. NB filters only pass through the wavelength they are designed for and nothing else gets through, UHC is broadband type filter and all you achieve by combining the two  is extremely long exposure times for imaging. BtW EQ5 pro is a very capable mount, since upgrading from EQ5 pro to HEQ5 pro I have failed to detect any improvements in either guiding or accuracy of the go to, it all depends on the balance of the scope and the accuracy of the polar alignment.

A.G

[kaymado]

Can't answer your filter question but I think you underestimate your mounts capablities Kay,have a look here to give you an idea on what's achieveable with your EQ5/200PDS

http://astrocasto.blogspot.co.uk/

Oily, I already know I can achieve impressive things as you did! I did try to get the bare minimum afterall Now i just need expertise and practise I guess.

But are your photos just done with camera and scope and modded camera?? no Ha or Oii filters?

As for your AstroEQ mod, I have considered doing this too. Does it not slew very slowly when you chose a target? I would have though 8x is the maximum speed of the motor.

I've modded the 450D myself too, bought a cheap one off ebay for that reason alone

Lensman57, thanks I believe that answers my question!

[Oily]

Oily, I already know I can achieve impressive things as you did! I did try to get the bare minimum afterall Now i just need expertise and practise I guess.

But are your photos just done with camera and scope and modded camera?? no Ha or Oii filters?

As for your AstroEQ mod, I have considered doing this too. Does it not slew very slowly when you chose a target? I would have though 8x is the maximum speed of the motor.

I've modded the 450D myself too, bought a cheap one off ebay for that reason alone

Lensman57, thanks I believe that answers my question!

My photos are just took with my modded camera and scope,only recentlly have I took some images with my Castell UHC filter fitted which has vastly improved my light polluted images.The AstroEQ slews at X64,it's slow but I can put it with that as I'm happy just to have a GOTO without breaking the bank

[ollypenrice]

I've just been working on a guest's Ha data from a modded DSLR. You only fire on one pixel in four but it's worth having. The camera must be modded, though, or the Ha won't pass. Yours is, so that's fine. The fast F ratio will be a bonus.

Olly

[kaymado]

You only fire on one pixel in four but it's worth having.

Olly

Thanks for the advice but could you please elaborate on this comment? I'm not sure I understand...

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[Pete Presland]

i think the comma corrector is essential it was the first thing i purchased for mine along with the T ring to fit it!

[poogle]

Thanks for the advice but could you please elaborate on this comment? I'm not sure I understand...

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I think Olly is referring to the bayer matrix used in DSLRs. It devides each pixel on the sensor into either red, green or blue in order to obtain colour images (there are two green squares in the matrix for every red and blue square).

Since Ha is collected by the red pixels only, the other three pixels are not helping with collecting the Ha data. This also means that since each pixel is either red, green or blue this design "discards" ~2/3 of the incoming light.

Hope this helps

/Patrik

[frugal]

I think Olly is referring to the bayer matrix used in DSLRs. It devides each pixel on the sensor into either red, green or blue in order to obtain colour images (there are two green squares in the matrix for every red and blue square).

Since Ha is collected by the red pixels only, the other three pixels are not helping with collecting the Ha data. This also means that since each pixel is either red, green or blue this design "discards" ~2/3 of the incoming light.

Hope this helps

/Patrik

Also the filters inside the camera are filtering out 75% of the Ha wavelength. So even the red sensors are only receiving 1 photon in 4 that arrive at the scope

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