C14 Moon

[matt_baker]

At our observatory we too have a C14 (non-edge) and it is an incredible piece of equipment, however I feel like I'm getting some underwhelming pictures of the moon in comparison to others I've looked at.

I was wondering if anyone could give me some tips on how to improve with the C14?

I have an ASI120MC that goes on a visual back. I also have a 2x barlow but seeing conditions are terrible to even attempt to use it

I've attached my most recent attempts, I feel as if the focus may be slightly off as I find the focuser to be terrible especially with the shift. Surely they would've come up with something better for a scope so expensive?

I used AS!3 for stacking and deconvolution on Pixinsight with unsharp mask and MLT

The sampling would also be okay with the barlow, but it's impossible to use with the seeing conditions again.

Thanks,

Matt

[kirkster501]

+1

Wondering this myself too.

EDIT:  Seeing was dreadful last night so don't beat yourself up if your concerns are on the basis of last night's efforts.

Edited November 9, 2019 by kirkster501

[Ibbo!]

Where is the C14 kept?

I have tried with a Meade 16" SCT housed in a dome and at the dome opening there was a "howling gale" (slight exaggeration)which I think was due to the heat from bodies computer etc escaping to the night air.
 

[matt_baker]

2 minutes ago, Ibbo! said:

Where is the C14 kept?

I have tried with a Meade 16" SCT housed in a dome and at the dome opening there was a "howling gale" (slight exaggeration)which I think was due to the heat from bodies computer etc escaping to the night air.
 

It's housed in a dome. Would there be a way around this?

Edited November 9, 2019 by matt_baker

[Ibbo!]

From home with my C11 I do not planetary image from the obshed but set up out side and sit away from the scope.

At a guess seperate warm room would be best.

Random thought block round the dome skirt and fully open the slit so heat goes out of the top.

Cut the number of bodies in the dome, when we did outreach it was oddly funny looking through the scope when somebody was stood in front of the scope and the dme opening esp at moderate power.

 

[matt_baker]

The only people who are actually in the observatory at any one time are my dad and myself, surely that can't be messing it up?

[paul mc c]

I would say it is probably down to bad seeing...and the bigger the scope the worse it will be.

 

[Peter Drew]

What's the visual image like by comparison at the time of imaging?   🙂

[Rusted]

Dome seeing! I'm a martyr to dome seeing. Except when I'm not.
My two story, entirely wooden, observatory building is open all around just below observatory floor level.
That's a 20cm or 8" wide open slot all the way around. The floor boards are deliberately gapped to provide air circulation.
An open, double door, down on the ground floor provides a chimney effect. Heat rises!

The dome skirt is deliberately leaky. A rubber skirt hangs down by its own weight and flaps in any breeze.
I have a large door to the west which can push the prevailing wind out through the observing slit if need be.

The dome and building are plywood covered to be thermally neutral. Low thermal mass and poor thermal absorption.
Badly spoilt by green [camouflage] paint! It ought to be highly reflective white!

I sit to the north of the pier at my imaging monitor. I wear highly insulating down clothing to slow body heat loss.
The open observing slit [beyond the zenith] should carry my body heat straight upwards and away.
Hopefully before it reaches the light path of the telescopes usually facing somewhere to the south.

Most observatories are built of thermally absorbent materials baking in the sunshine all day long.
Patios and buildings are even worse! They absorb the sun's heat and let it go again all night long.

So the dome, building, surroundings, mounting and instruments are very likely to be much warmer than [usually falling] ambient.
Excess warmth means a bonfire of the vanities of actually daring to own an observatory.
Now add extra human bods inside your "toasty warm" observatory. It can only end in tears. 🤣

[newbie alert]

It may take 2 or more hours for the thermals within the tube to equalise  if you kept it inside the house it may never equalise throughout the night..

Good seeing conditions are really rare, the jetstream needs to be well out of the way to have really good seeing conditions, just to have a clear night lately is a big enough ask!!

Just need to make sure that you're ready for those rare nights... collimation checked..get your focus spot on but don't chase the seeing.. I'm sure it will all come together it's just climate conditions ..

[Star101]

I would try again when the seeing conditions improve.

While waiting for the seeing to improve - Collimation is one thing to look at. Find a bright star first. Once happy it looks collimated. Try a dimmer star and check again. Also, check stars at the four corners of the image. Don't drive yourself crazy though lol.

I do find my C11 is great for deep sky stuff but always find it does not show the contrast that my APO shows when imaging the moon.

Good luck.

 

[Owmuchonomy]

Could be a whole host of things.  Assuming your collimation is sorted and the scope has cooled (a big problem in our climate with the C14) then my comments would be on your imaging setup.  Better results are obtained using a mono camera set up that has good near IR sensitivity and with an IR pass filter such as an 850nm version or similar.  This helps somewhat with seeing issues.  The 120 has an awkward pixel size too for your f/.  It should work ok with a 2x barlow though.  I find my ASI290MM with its smaller pixels and great near IR sensitivity gives best results on lunar work when using my f/10 9.25" SCT (or even my ED150).

[kirkster501]

Almost certainly your issue is seeing and/or collimation.  A big scope makes the seeing appear much worse. Also as Newbie Alerts says, if the C14 scope is kept inside and then taken outdoors it may never stabilise all night.  Big scopes must be kept outside in an obs or at the very least an unheated garage/shed.  Even then, the few degrees between outside and inside a [cold] observatory, the delta between the two can take an hour or two to stabilise adequately. you can see this when you look through the EP at the bubbles of air on the defocused star.   So you need to get the roof open with a big SCT as soon as you know you're going to be out.  This is not always possible of course depending on other commitments.

Damian Peach said in one of his talks he can get more good seeing nights in a five day trip to Barbados as he can in two years at home in the UK.

[JamesF]

There was a bit of a thing a few years back about wrapping large SCTs in insulation, the idea being that it didn't matter if they weren't at ambient temperature as long as they were at the same temperature everywhere.  I've no idea if it's become regular practice or if the idea died a death.

James

[knobby]

As James said, I've seen that suggested before somewhere, it apparently stops the air movement inside the tube ...

Worth a bash I guess.

[JamesF]

7 minutes ago, knobby said:

As James said, I've seen that suggested before somewhere, it apparently stops the air movement inside the tube ...

That was the reasoning I recall, yes.  I think the claim was that the upper part of the OTA, facing the cold sky, loses heat faster than the lower part that is facing the (warmer) ground, so air in the upper part cools more rapidly and creates a convection effect inside the tube.

I can't recall whether anyone posted any definitive measurements to show whether the insulation helped or not.  Having had to put my C9.25 away for a while until I got the observatory built, I lost track of developments a bit.

James

[matt_baker]

Not sure if these are much of an improvement but I managed to get out last night and take these

Also since it's a mono cam and all it has is a clear window, what filter should I be using for the moon?

Edited December 4, 2019 by matt_baker

[Rusted]

The image scale is extreme. On a "lunar orbiter" sort of scale.
A bigger sensor would help but at much greater cost.

The guiding, focus, mounting alignment, collimation, cooling down and seeing conditions would have to be spot on.
[Not necessarily in that order.]

The Moon is very low at the moment. Which does not bode well for perfect seeing conditions.
I was only using 2.2m fl two nights ago 180/12 and the results were absolute mush!

As to filters: The usual recommendation of Solar Continuum will make your image darker and fps much slower.
Noticeably so in my case.

Edited December 4, 2019 by Rusted

[matt_baker]

It was at about 30 degrees for me last night which is much higher than it has been over here.

I think when I know it's clear, I'll go over and open up the dome and scope to let it acclimatise and cool to ambient(ish)

How much would having the dew heater turned on hinder the seeing, since I've been having issues with the inside of the corrector dewing up?