Slightly bigger but still blury Mars

[Darth Takahashi]

Here is Mars imaged last night in between breaks in the thin cloud cover. Pushed a little harder with a 2x barlow, so the telescope was operating at F24 or 6000mm focal length.

I believe the only way forward now is with a mono camera and an IR pass filter to improve the image detail at least. Might experiment with eyepiece projection when time permits and the weather improves.

Telescope: Mewlon M250

Camera: Philips SPC900NC webcam

Mount: Gemini G41

The weather conditions seem to be imposing the limitations at the moment and an IR pass filter might be the only way forward.

Neil.

[Clayton]

You have some nice cloud detail there Neil. And unfortunately the boring side of Mars. I don't think it's such a bad shot

I'm not suggesting that the following are related to your performance limitations, but the ultimate quality of the optics, collomation, focus, and seeing, will all have an effect on your image, The IR Pass filter will help with seeing, and lot's of practise, with focus. But you may be dissapointed with a mono camera unless you are certain that your optics are in top shape.

[dweller25]

That is exactly how I saw Mars last night.

Around 7PM seeing was very good but deteriorated to quite poor very quickly after that.

There was a hugh amount of moisture in the atmosphere (not rain !!!)

Given the seeing conditions that's a good image.

[neil phillips]

Hi Neil, Nice shot,

Clayton is right, but unless something has happened to your scope, thats one hell of a scope, im sure you can push the Mewlon a lot harder than 6000mm even with a spc, i know seeing plays a part, but thats one scope ive seen some very high power images, it takes practice to get to 10.000 mm routinly. but with sharp focussing even just a average night will reveal a lot of detail, i set the spc at 18000mm fl at the slowest exposure it could do. gain about 70- 80% with a 10 " newt those settings should work. but often around the 10,000 mm mark its tighter for sure. Pete is the master of mag. A lot of people seem cautiouse as far as pushing FL is concerned. even if you get 1 shot out of every 4 nights, the detail will increase.

K3ccd tools is good, at capture you have a level meter which i set to 150 160, which seems low, but is actuallly quite strong, especially 160. Not sure if collimation is a consideration with the Mewlon, But its a supreme instrument that. I think 10.000mm fl is a good target, even with a spc colour. It just takes practise.But you certainly have the optrics for it. That would be one of my legend scopes, the DMK is a great camera.

[Darth Takahashi]

Thanks for the encouragement, I'll try to push the Mewlon harder when the weather permits. I think I'll try stacking the Extender Q with the barlow which will get me to 9000mm focal length. I also just picked up a cheap TRUST webcam with 1280 x 1024 pixels, so I'll give that a try too!

I don't believe collimation is an issue and once the scope has acclimatised its focus doesn't drift. I am making an artificial star since the weather conditions don't permit reliabile collimation against stars, at least not easily.

My frustration is that the equipment is good enough, my technique needs to improve but the weather is killing me!

I have the feeling that if lived in Selsey it would be like shooting fish in a barrel ;-)

Neil.

[neil phillips]

The settings become easy once you try shooting for powers sake, although i would like a lightning fast exposure at 10 Metres FL with a spc and 10" scope its just not possible,

so you end up setting the signal for the power, whatever that is,

if you can get a good signal with a slightly faster exposure, then go with that, cant remember what the slowest exposure on the spc is, but at 9000mm you most like will be on the second to slowest exposure speed,

gain way up between 60 and 80% Go for as long a capture as you think will not show bad rotation. At 9000mm personally i dont think 5 mins would be bad at all, you need lots of frames. Most would see that as upper limit, you can always chop the beggining or ending off, so if the ending is a worse part of the capture then chop that, couldnt do that on a 3 min capture window at 10 fps.

signal strength can not be underestimated, if its low the captures will lack vibrancy, colour detail ect, too high and areas burned out. the optimum i think is just outside burnout, on the level meter on k3 for a 10" its about 160.

with these settings at 9000mm fl, good focus, saturation about midway, reasonable seeing. your Mewlon should really deliver.

[Darth Takahashi]

The SPC900 is currently running at around 55% in brightness and 33% gamma with the 2.5x barlow in place, so I guess I can still push harder. Im using wxcapture to gather the data from the camera. I can switch to KCCD3 if its a better solution. The level meter sounds like a nice option to have.

I did some quick pixel maths to check the effective focal length and concluded the barlow is actually giving around 3.65x the focal length, so around 10952mm. I'm doubting that this is correct!

Mars is approx 128 pixels in diameter in the image and its current angular size is approximately 13 arc-seconds, therefore, the resolution is approx 0.10156 arc-seconds / pixel with 5.4 micron pixels, correct?

This seems like a lot already?

[neil phillips]

Not sure on the figures you mention, but your image scale looks reasonable, compared to what im finding was a good power at mars current small size, with a 10" newt, my scale looks about a third higher, or bigger. it seems to be definition thats a problem, gamma i would set to zero, brightness midway contrast midway, gain at about 70% with as fast a exposure as you can muster with a 70% even 80% gain, should give good definition if your collimation and focusing is good, your stack looks noisey but definition low. like you didnt capture a lot of frames, so im not sure about that. But seeing may also have been bad,

I agree if your image lacks definition then raising the power may not help.

you need to tackle the definition, and im unsure whats causing the problem, but the main culprits usually, are seeing, collimation, focusing camera settings, not always in that order.

i would think, what of those do you belive you could work on. or is the weak link. if you can figure that out , it will help. i sucspect its one, or a combination of those Neil.

But im guessing of course. your scope interests me. ever since i first learned about them.

[Darth Takahashi]

I made an avi of approx 2000 frames, about 1.4GB. However, the seeing was terrible, Mars was jumping about 15 to 20 pixels all over the place, maybe even a little more.

Of the three issues that you raised above we can rule out collimation. I have checked it during the day and on stars at night and do get concentric rings, but as a perfectionist someone might argue that the power I'm using isn't high enough! 22mm eyepiece directly in the back no diagonal (136x). The problem is if I push harder the seeing isn't good enough to collimate the scope. So this is a measure of the seeing at my location, hence I will make an artificial star at some point.

Focus is a tricky one to answer! starting out at 136x the diffraction spike run through the centre of Mars. Bang in the WO 2.5x barlow and the diffraction spikes are gone, so I use the edge of the planet to determine the best focus on the computer screen. I have tried a Hartmann mask once at focus and it seem to confirm that I'm at focus. If there is a better technique I'd appreciate the advise.

Webcam setting, yes here I believe I can gain some extra definition with a few better tweaks.

Thanks for all the info so far, best regards

Neil.

[Taff]

Hi Neil' That's a nice capture of Mars' with the ploar cap on show.Mark

[Darth Takahashi]

Thanks Mark, but I still have some way to go to get closer to the high standards set by others here, I guess the important thing is to keep trying... weather permitting of course ;-)

Neil.