Planetary imaging strategy

[GlassWalker]

With the recent addition of an 8" SCT I want to have a good go at Jupiter and other planets when they become visible, but I'm debating the best way forwards.

Currently I have two cameras that could be used for imaging. The main camera is a DMK41, but at 15fps I'm also not making the most of its sensor area. My other camera is the QHY5. While also 15fps at full resolution, it is supposed to do 50fps at 640x480 but I haven't figured out exactly how to do that yet.

I do want to move to colour. So my choices are:

1: stick with the cameras I have, get a filter set and wheel. Let's say, a budget RGB filter set and filter wheel will cost around £200 total. I would not need the filters or wheel for other imaging. Well, ok, I might use it for the moon too as a low priority, as mono moons look a bit dull.

2: get a different camera. If I get a colour one, like a QHY5v or QYH5t (or other model?), I wont need the filter set or wheel. Either of those cameras are under £200 also. I guess this would end up lower resolution, but I'd not have to worry about colour alignment during processing.

Any suggestions or comments?

[JamesF]

The cheaper RGB filter sets tend not to be parfocal which could be a pain in the neck though not the end of the world. It's probably not the greatest option if you're trying to do LRGB images of Jupiter, trying to capture all channels within a three or four minute period and having to refocus between filters though.

Resolution isn't everything. It's more important that you can get enough light on the pixels for the sensor to work well, and there's no point having far smaller pixels than the smallest thing the scope can resolve. In fact, the increased sensitivity of slightly larger pixels may be a benefit.

My own inclination is probably to end up going to monochrome at some point and the DMK21 may be the obvious choice in that case, but I'm not convinced that it really offers value for money so for the moment I'm sitting on the fence.

James

[GlassWalker]

If I went the colour filter route, I'd skip L, just do RGB.

Thinking more, absolute pixel size is irrelevant providing I can adapt the optics to suit. As it's a fixed aperture, varying focal length for a given field of view per pixel, the focal ratio must also change so the light gathering per pixel will remain constant. Basically I can choose the resolution in either case. My earlier statement in 1st post would only hold true if you did not modify the optical chain to compensate.

So the trade off is a colour sensor would give lower per pixel noise in a given time, at lower resolution. I can jack up the focal length to offset the resolution loss, which would slow the focal ratio and negate the potential noise benefit. So on that train of thought, either option would work out about the same quality per time anyway, but using a colour sensor would cut out some processing steps!

With that decided, I just need to decide on the camera... have to say from what I've seen of the QHY5 I really don't like their bundled software! I need to see if alternate software can provide better control.

[FarSide]

My advice is go the filter wheel route. When you use color instead of mono you lose a ton of resolution; the loss of quality in the captures are pretty evident. There's no point really in avoiding the processing steps if your captures that in all fairness will be mediocre. With a mono you will be able to have extremely good resolution levels and with a filter wheel within your imaging trail you'll have color also. The best of both worlds.

Be aware though, using a filter wheel while photographing will take some practice. Jupiter for example starts to smear badly after just two minutes of photographing because of it's massive rotation speed - so you need to be well practiced in getting all of your RGB colours done within the two minutes. It's alot to learn, the processing takes time but the results are well worth the effort - just look at Damian Peach.

Edit: Also the DMK only really works well on dim planets; Jupiter and Saturn for instance are quite dim especially on their limbs; 60fps is common. That said, brighter bodies like the Sun and the Moon will require higher frame rates that the DMK just can't manage and so a Flea3 comes in handy when photographing our more showy solar bodies with it's 120fps top rate. Flea 3 do mono and color cameras though only the mono has the appropriate CCD chip.

It took me a long time to decide which direction i wanted to go in with planetary photography - mono is the way to go no question.

Goodluck.

[riklaunim]

You can do solar and lunar imaging with the DMK21 - but at 60FPS.

[GlassWalker]

I'm quite tempted with the DFK21.AU618 or whatever its called. All the more so if you need to do the whole capture in 2 minutes. While I haven't looked into it in detail, I thought there's time for at least a minute per colour sub without too much pain. De-rotation sounds like more fun than I'm motivated for right now...

Forget solar/lunar from this discussion for now, I already have the DMK41 for that.

I did have a go with a colour camera on Jupiter tonight, the ancient Meade LPI I had lying around and never seriously used before. Possibly because I never really figured out the software...

Meade's software set to only capture frames above 50% quality. Tidy through PIPP and stack in AS!2, the latter set to 75% stack of 121 files, 1.5x drizzle. Wavelets in Registax 5. I really want a bigger barlow...

[GlassWalker]

Ok, I might do more U-turns than the current so called government, but I've just sourced and placed an order for a cheap filter wheel and RGB filter set. Will see how that goes...

[JamesF]

Ok, I might do more U-turns than the current so called government, but I've just sourced and placed an order for a cheap filter wheel and RGB filter set. Will see how that goes...

What have you gone for, out of interest?

James

[GlassWalker]

Baader absorptive RGB+IR block set and unbranded 5 position filter wheel, and some other accessories that always seem to add up...

Suppose I should figure out how to use the QHY5 at 50fps before the next chance.

[FarSide]

Is 50fps it's stop spec, Glasswalker?

[GlassWalker]

It's 15fps using the full sensor, and supposedly up to 50fps in crop mode. Just not sure how to use it yet...