ASI178 A good choice for planetary imaging?

[DrRobin]

Hi,

I have recently changed from a C11 (which I used with a 2x barlow for the planets) to an RC250, so dropping from fl=2750 (or 2x this with a barlow) to fl=2000mm.  I can't fit my 2x barlow on the end of the RC250 without it hitting the obs wall, so a couple of choices to get more resolution:

1) Fit a diagonal; or

2) An ASI178MM with 2.3um pixels.

I realise that the small pixels will mean longer exposure times than my ASI120MM (3.75um) without a barlow, but should actually be quicker than when a 2x barlow is used.  However, a barlow only really reduces the effective pixel size in any case.

I am hoping to use  this camera to get better resolution on the planets with a scope at F8 (fl=2000mm) without a barlow.  I don't really like the idea of fitting a diagonal, although a good quality one shouldn't be an issue, right?

Is there anything else to consider about small pixel sizes or should I be looking at a different camera? 

TIA

Robin

[michael.h.f.wilkinson]

I am not sure the rolling shutter of  the ASI178 is ideal, but I have seen some impressive results with that camera on the moon, so it should be OK. You will need to use ROI mode to get really high frame rates, but that is certainly possible

[DrRobin]

Thanks Michael,

I am not really up to speed on the difference between rolling and global shutter, I know that rolling shutter can give motion blur, but would it be noticeable on say Jupiter with exposure times of, say 10ms?

My main interest is in pixel size, it is only 60% of my ASI120 and less than half of my ASI174.  I regularly use ROI on my ASI120 so that wouldn't be a problem and don't normally get exposures of less than 10ms so 100 fps is about my max.  I do use 16 bit mode though.

ASI174 has become my main solar cam, which works well, just looking to improve on the dark side now.

Robin

[riklaunim]

Older sensors did have some issues with rolling shutter, but newer do not as for now.

I have 178mm and it should be quite good fo lunar/solar as well as planetary. Low noise and good performance.

[DrRobin]

18 minutes ago, riklaunim said:

Older sensors did have some issues with rolling shutter, but newer do not as for now.

I have 178mm and it should be quite good fo lunar/solar as well as planetary. Low noise and good performance.

Perfect, many thanks for the reply.  I might give an ASI178 a try.

Robin

 

[Freddie]

I guess the other question is, which planets are you going to image given their positions over the next few years?

[DrRobin]

Jupiter, Saturn, Mars?

Jupiter is fine at the moment, I know Saturn will be a bit low but still visible and Mars must be coming round again soon?  Anyway if it doesn't work out it will get used for solar, I am going for the mono version.

Robin

 

[riklaunim]

Next year only Jupiter, and after that for few years nothing except of Uranus and Neptune unless you are on southern hemisphere.

[DrRobin]

19 hours ago, riklaunim said:

Next year only Jupiter, and after that for few years nothing except of Uranus and Neptune unless you are on southern hemisphere.

Hmm, see what you mean, everything is getting low, I think I will put a new camera on hold.  Good job I decided to go back in to DSO imaging....

Robin

[michael.h.f.wilkinson]

I will still be imaging them, even if they are low. It's what I got my atmospheric dispersion corrector for. That doesn't solve all problems of course, but I will keep at it (and head south for the holidays, with all the kit in our good old Renault Espace.

[riklaunim]

178 can do IR imaging of uranus and neptune. There is also moin and sun. Plus those new cameras can do DS lucky imaging.

Going even more into lunar - you can use specific petrographic narrowband filters on the moon too. That gives moon in false color that reveals age and composition.

[DrRobin]

Hi,

I have a Starlight Xpress for DSO, so no need to buy a new camera. 

I can view down to about 15 degrees above the horizon so Saturn will be fine this year, Mars is also possible, but as you say next year only Jupiter and then the year after not very much to go at.

How long does this last for, a few years I am guessing?

Robin

[riklaunim]

Yes, few. You can check in stellarium.

[Steve Ward]

Saturn continues to drop until 2018 before starting to climb again ... 

[DrRobin]

Given all of the above, I thought I would have a go with my 2x barlow.  To make it fit inside the obs, I had to put a mirror diagonal in and tonight was the first chance I got to test it.  Sadly it was a bit too windy and the seeing wasn't the best but I pulled this RGB image out of 25% from 2000 frames.

I am quite pleased with the result and look forward to a better night.

Robin