Barlow recommendations for planetary imaging

[edarter]

Hi,

I know my gear is far from ideal for planetary (sw130pds and eos 600d) I've seen posts recently where people are getting reasonable results out of similar gear. What would be a good Barlow to use if I were to attempt this? And what kind of results could I expect?

Thanks

Ed

[Nicola Hannah Butterfield]

I used the kit Barlow on this on my 200P, with a Canon 6D, so I guess a 3x might be better suited for the 130PDS, as to quality I will leave that to others.

Edited November 23, 2022 by Nicola Hannah Butterfield

[Neil_104]

I don't do a massive amount of planetary imaging myself, but I believe the magic formula is to aim for an f ratio of 5 x the pixel size of your camera. I've done a quick check on specs and that would be 5 x 4.3 = 21.5. So with the sw130pds you'd need at least a 3x to be getting close to that f ratio. I'm sure someone will correct me though if I have that wrong  I'd expect though that to begin with, ensuring accurate focus, imaging on a night with good seeing and good post-processing will give better improvements than say a TV barlow vs a more entry level one. Good luck!

Edited November 23, 2022 by Neil_104

[vlaiv]

Just use whatever barlow element is cheapest for you / you can most easily get.

You can vary magnification of barlow by changing the distance between it and sensor (closer to sensor less magnification, further away from sensor - more magnification, just add some sort of extension tube) to dial it in to suit your needs.

Here is a good one:

https://www.firstlightoptics.com/barlows/astro-essentials-125-2x-barlow-with-t-thread.html

you can add T2 extension between it and camera T2 adapter, but by the looks of it, if you attach it directly with T2 ring to DSLR body - it should already be at about x3 or so. If you find that you have too much magnification - barlow element detaches and has 1.25" filter thread - which you can use to connect it to shorter 1.25" nosepiece that has t2 thread and so on ...

Camera will be limiting factor for you, and if you are even a tiny bit serious about planetary imaging - it is better to invest into planetary type camera.

 

[windjammer]

Its worthwhile playing with eyepiece projection as well, with or without a barlow.  You will probably have to dip deep into the junk box, ep projection needs lots of extension rings to finagle something together.  Also a collection of eyepieces to experiment with to find the sweet spot.

On image size, try and get the planet disk as big as possible, compatible with keeping it in the frame as it bounces around, and bright enough so that short exposure times (video rates if you can manage it, 1/25or 1/50 s) give a good signal to noise.  I always think something like Registax can pull amazing detail out of a few thousands subs, and the more pixels it has to work with the better.  Sub rayleigh resolution detail is possible. 

Getting a planetary camera is good advice - it doesn't have to be cooled or have a huge sensor, so not too expensive.

My 2 bits.

Simon

 

 

[ONIKKINEN]

Does the 600d have a "movie crop" video mode that shoots 640x480p uninterpolated video? If it does, you can use that to shoot 50fps video for planets. That mode is compressed however and the resulting stack will have artifacts because of that, but you could use Magic lantern, a 3rd party firmware package for canon cameras, to unlock raw video mode that does not have any compression. Framerates will likely suffer a bit towards the 30-40 range but its still better.

I have done that with a 550d and while the captures at the time were not amazing, it did work as a planetary capturing tool. Maybe give that a try if 600d also has the possibility to do that?

As for the barlow, you will want to be in the f/17-f/20 range for ideal sampling with the 600d. I would try a 3x barlow, that will probably be more like 3.3-3.5x with a DSLR since the sensor to barlow distance will be quite long with the camera body, T-ring, nosepiece combo eating at least 70mm of backfocus.

[edarter]

Thanks all, I shall do some more digging on this using the sage advice given above!

The 600d does indeed have the cropped video mode and mine is also upgraded to magic lantern, so I should be good to go on that front once I get my head round what it actually all means 😀 

Ed