Is there such a thing as photography Barlow?

[DJScotty]

Hi all.
I hVe a ts102 f7 scope.
Putting aside the obvious issues of imaging at f14 and the possibility of field curvature is there such a thing as a Barlow lens that is suited to astrophotography?
I have had a little look at the ts website and there are a couple of possible candidates. I would assume 2 or even 3 inches would be necessary.
I know it won't be cheap if it exists
Thanks
Scott

[Atmos]

I believe the TeleVue Powermate series are designed for enough correction for AP :)

[Slawomir]

Astro-Physics has a 2" Advanced Convertible Barlow for small to medium size chips for about US$250.

And then there is ultimate Baader Fluorite Flatfield Converter Barlow that covers a full frame sensor. But is will easily be around AU$1000 landed.

[multiweb]

I swear by the Baader FFC (http://www.astro-physics.com/index.htm?products/accessories/baader/ffc).

[DJScotty]

Thanks for your suggestions. Plenty of food for thought. The baader ffc looks like the best way to do what I want.
And certainly cheaper than a new esprit 150! :lol:

[Peter Ward]

I have used both. the AP imparts very little vignetting, but off axis is not particularly sharp.

The Baader FFC ( $A1325.00 landed with GST) ...well....expensive yes...but... is amazingly sharp....just perfect really.

[Merlin66]

+1 for the TV Powermates.
I use them all the time for solar imaging.

[multiweb]

I thought at first getting a range of televue barlows then realised by the time you get the set it costed more than the FFC for lower quality. The FFC gives you x3 to x8 all in one. Nill light scattering, no reflections, no chromatic aberrations whatsoever, it is perfect. When you look at it this way it is the cheapest alternative. If you only require x2 or x3 or x5 then you can save some money and go televue. If you're thinking you might need other magnifications then the FFC is your all in one barlow.

[lazjen]

I'm curious - what, if anything have you used x8 on and what was the setup?

[Atmos]

Might be good for planetary with a Newtonian, especially if you have an F/4 dob.

[multiweb]

Never went to x8 for DSO. Max I went was x5 but I'd say you could use x8 for planetary or other although it would depend greatly on the seeing. Here's a couple of pics:

90mm triplet native FL ~650mm barlowed x3 (https://onedrive.live.com/?authkey=%21ACnUIS_stUVCu-s&cid=6930D3AD12D5044C&id=6930D3AD12D5044C%211349&parId=6930D3AD12D5044C%211059&o=OneUp) vs. prime focus field (https://onedrive.live.com/?authkey=%21ACnUIS_stUVCu-s&cid=6930D3AD12D5044C&id=6930D3AD12D5044C%211132&parId=6930D3AD12D5044C%211059&o=OneUp).

FSQ native FL ~530mm barlowed x3 (https://onedrive.live.com/?authkey=%21ACnUIS_stUVCu-s&cid=6930D3AD12D5044C&id=6930D3AD12D5044C%211531&parId=6930D3AD12D5044C%211059&o=OneUp) vs. prime focus field (https://onedrive.live.com/?authkey=%21ACnUIS_stUVCu-s&cid=6930D3AD12D5044C&id=6930D3AD12D5044C%211515&parId=6930D3AD12D5044C%211059&o=OneUp).

The first pic I saw taken with an FFC blew me away. It was an Ha shot that Peter Ward took years ago in the keyhole area at a ridiculous FL 4m or 5m from memory with his RC and that sold it for me.

[alocky]

ASA make a 1.8x imaging Barlow, with the delightfully descriptive name of OKORRB. I've used it on a 10" F4.5 and was very impressed.
http://www.astrobin.com/287850/
Cheers
Andrew

[DJScotty]

That's a great image.
That might be an option.

[Slawomir]

I might be wrong, but x8 makes sense with a large aperture, but a 4" has a more restricting Dawes limit. There is only so much one can extend focal length with a 4" aperture before diffraction will put a cap on maximum resolution. That's how I understand it anyways.

[Merlin66]

the rule of thumb is focal ratio "optimum"= x5 the pixel size.
This generally means ratios around f25 to f30.
If you have a f5 scope, then x5 is pretty close.
If you can find a TMB x1.8 barlow, you'll be impressed.