Achromat for NB? Advice please!

[pluto (Hugh)]

At the moment I have an f7.5 SW ED80 APO and it's great. But I'm now imaging narrowband and I noticed the SW102 f5 achromatic, like this one: http://www.bintel.com.au/Telescopes/...oductview.aspx (Andrews has the OTA only for $299)
So I'm thinking that it would be nice to have that slightly wider FOV and larger aperture so I can acquire more light more quickly.
As I understand it, because I'm shooting NB (7nm), I shouldn't experience the usual achromatic limitation of different wavelengths not coming to focus together.
So my questions are:

1. Am I thinking along the right lines or am I way off?

2. In terms of imaging NB with my Atik 314L+ will the optical quality be as good as my SW BD ED80?

3. Would I be better off getting a 0.8 reducer to bring my ED80 to 480mm f6? (or a similar reducer)

4. Is the focuser any good on the SW102? If not would it need to be replaced or could I get away with using an electric focus drive to get more accuracy? (like this one which I was thinking of getting anyway: http://www.bintel.com.au/Astrophotog...oductview.aspx)
- I guess I could just swap the focuser over from my ED80?

5. Does anyone know how heavy this scope is? Or more importantly, how much heavier than the ED80 it is? The ED80 is currently well suited to my EQ5 and I don't want to get a heavier mount at the moment as I have to carry it everytime I use it.

I'm just thinking that for a relatively small amount of money I could be getting a fair bit more image in less time. Either way I won't be getting rid of the ED80 any time soon, maybe it's just the cloudy nights lately have given me too much online window shopping time

[Mighty_oz (Marcus)]

Originally Posted by pluto

At the moment I have an f7.5 SW ED80 APO and it's great. But I'm now imaging narrowband and I noticed the SW102 f5 achromatic, like this one: http://www.bintel.com.au/Telescopes/...oductview.aspx (Andrews has the OTA only for $299)
So I'm thinking that it would be nice to have that slightly wider FOV and larger aperture so I can acquire more light more quickly.
As I understand it, because I'm shooting NB (7nm), I shouldn't experience the usual achromatic limitation of different wavelengths not coming to focus together.
So my questions are:

1. Am I thinking along the right lines or am I way off?

Can be done, been there with sw120 f5 not as good as an apo

2. In terms of imaging NB with my Atik 314L+ will the optical quality be as good as my SW BD ED80?

Probably not, they're good scopes the ed80's, also had one.

3. Would I be better off getting a 0.8 reducer to bring my ED80 to 480mm f6? (or a similar reducer)

If u get a good reducer

4. Is the focuser any good on the SW102? If not would it need to be replaced or could I get away with using an electric focus drive to get more accuracy? (like this one which I was thinking of getting anyway: http://www.bintel.com.au/Astrophotog...oductview.aspx)
- I guess I could just swap the focuser over from my ED80?

If your serious about imaging and don't want to manually refocus after every few images then automated is the way to go. Will cost u tho.

5. Does anyone know how heavy this scope is? Or more importantly, how much heavier than the ED80 it is? The ED80 is currently well suited to my EQ5 and I don't want to get a heavier mount at the moment as I have to carry it everytime I use it.

2.5kg according to http://www.skywatcher.com/swtinc/pro...1=1&class2=103

I'm just thinking that for a relatively small amount of money I could be getting a fair bit more image in less time. Either way I won't be getting rid of the ED80 any time soon, maybe it's just the cloudy nights lately have given me too much online window shopping time

Best to stick with the ed80 until u get serious they produce great images.

My 2c worth hope it helps.

Marcus.

[Lee]

You can image narrowband with achromats perfectly well, you just need to focus in between filters (no big problem, would be good practice to do so with an apo anyway).... I did the same in 2007, bought a 100mm f/5 for narrowband....
I have both an ED80 and a 100mm f/5 Skywatcher achromat, I haven't weighed them, but I doubt any weight differential would be more than 10%....

Not a bad scope really, the focuser is a bit ordinary though, to be expected for the $$....

I'd say go for it, a cheap venture in the scheme of AP! I use mine as a guidescope now (got aperture fever).... there is always the 150mm f/5 too....

[pluto (Hugh)]

Thanks Lee!
My filters aren't parfocal so I have to refocus anyway and I've had lots of practice

Thanks Marcus, I am very happy with the ED80 and I'm pleased with the results I'm getting but I do wish the FOV was a little bit wider with my CCD.

[Tandum (Robin)]

The lower F ratio will give you more sky and the bigger hole will give you more light. Sounds like all positives to me. I'd swap, it's a no brainer.

[JohnH]

You may find the build quality and in particular the focuser on an Achros too be unsuitable for AP work. I suspect you will need to automate focus or this will drive you nuts. Putting a nice strong motorised usb driven focuser and a nice CCD on a cheap ota seems a bit of a false economy to me maybe a bigger ED semi apo?