Barlows And Astrophotography...

[Ian McCallum]

I'm drawn towards the ZWO ASI 224MC for planetary photography.

My two telescopes are a Sky-Watcher Classic 200P Dobsonian and Evostar 120 achromatic refractor.

Based on their focal length, it looks like I'd need either a 2x-2.5x Barlow.

Any suggestions that isn't going to break the bank? 🤔

[discardedastro]

Really depends how you want to image!

If you're happy hand-guiding etc then consider something with smaller pixels/sensor to get a narrower FOV and stick to the Dob - you don't need big light-bucket pixels for planetary.

You could pop in a Paracorr or similar barlowing coma corrector to give improved coma performance as well as a mild barlow - lots of APs use Paracorrs and similar without issue on Newts/Dobs. Paracorrs are pricey though, so might be better off going down the pure Barlow route which can also work well. Second-hand Televue Powermates can be had from time to time if you're patient, but they're £300 new for 2"; I've heard good things about the ES barlow at around £200, though.

I'd definitely consider what you might want to do in future, though. Barlows are definitely one-trick tools - I haven't touched mine except to use it in collimation in over 2 years, since I've not been trying to image targets that need it.

[johninderby]

The ES or Altair focal extenders are very nice amd great performers. Very similar to a Televue Powermate in performance. They do 2x, 3x and 5x.

https://www.harrisontelescopes.co.uk/acatalog/explore-scientific-2x-barlow-focal-extender-1.25-0218750.html#SID=564

https://www.harrisontelescopes.co.uk/acatalog/altair-lightwave-2x-flat-field-tele-extender.html#SID=564

Edited January 29, 2022 by johninderby