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Terrible Jupiter w/Ganymede 2022-07-04

Planet Maksutov DSLR Astrophotography
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#1 BQ Octantis

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Posted 04 July 2022 - 07:32 PM

An hour after my awful Saturn shot, I turned my scope to Jupiter. Details on the surface on which to focus were hard to come by, so I had to go with the planet's edge. Jupiter's available features were banal to begin with, so the result was less than meh.

 

post.jpg

Jupiter w/ Ganymede 2022-07-04 08:11 UTC

Skywatcher Mak 180

Fujiyama 12.5mm ortho

Canon 600D/T3i

 

When I brought my rig inside, there was all this wetness everywhere that I literally never had in 5 years of imaging in the Australian Outback. What dew you reckon that was? And dew you think that affected the image at all?

 

BQ

 

P.S. Dew shield is on order…


Edited by BQ Octantis, 04 July 2022 - 07:35 PM.

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#2 Stellar1

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Posted 04 July 2022 - 07:39 PM

I couldn't "like it" cause it just looks like I'm supporting you kicking yourself. Planetary imaging is a craps shoot, I aim my scope and mash buttons, sometimes they come out good and sometimes not so good. I see lots of detail there.



#3 Look at the sky 101

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Posted 04 July 2022 - 07:41 PM

I think it's beautiful shot. 



#4 yock1960

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Posted 04 July 2022 - 07:54 PM

An hour after my awful Saturn shot, I turned my scope to Jupiter. Details on the surface on which to focus were hard to come by, so I had to go with the planet's edge. Jupiter's available features were banal to begin with, so the result was less than meh.

 

attachicon.gifpost.jpg

Jupiter w/ Ganymede 2022-07-04 08:11 UTC

Skywatcher Mak 180

Fujiyama 12.5mm ortho

Canon 600D/T3i

 

When I brought my rig inside, there was all this wetness everywhere that I literally never had in 5 years of imaging in the Australian Outback. What dew you reckon that was? And dew you think that affected the image at all?

 

BQ

 

P.S. Dew shield is on order…

One thing you 'dew' count on in the US, east of the Mississippi anyhow, is dew. My scope always has a dew shield on, unless it's breezy enough to keep dew from condensing on the corrector. Sometimes I'll scratch my head as to why things start to go dim 'all of a sudden' , then I'll check and likely find dew as the culprit. I've got a dew heater...but dislike using it, since if not set just right, it can cause problems with image quality. 

 

Steve


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#5 Kiwi Paul

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Posted 04 July 2022 - 08:07 PM

Hi BQ
Well that shot is reasonable given the conditions.
I took a close blown up look at that moon and boy it’s about as symmetrical as it could be, so your collimation appear to be spot on!
You’re not in an area where the boundary layer is drier than popcorn fart as in the Outback! I have a problem with dew most days so I started out looking for some of that say 10mm rubber foam to coil up into a cylinder to pop over the front of the scope. Before I found that, I came across some 2mm thick felt. So I bought a couple of metres of it and wound it into a cylinder with areas of that pvc wood glue between the layers to hold it together. It works like a charm. I will send a picture separate to this post because I’m on my phone right now.
I hear people talk about humidity affecting their imaging, but apart from dew, I can’t see how it would. Perhaps the transparency is lowered somewhat. That is what happens on the way to fog formation.

Cheers Paul

#6 Kiwi Paul

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Posted 04 July 2022 - 08:24 PM

Here is the shot of my telescope with the felt dew shield. As Steve says he and I have it on the telescope pretty well every imaging session. Sometimes dew may form (see signal drop on histogram) but a blow with a hair dryer will clear it quickly and conditions return to settled fairly quickly.

 

Telescope with felt dew shield.jpg

 

As you may guess the front end corrector plate is located about half way up the tube, the rest is protection from dew. Having it fit the telescope so far down keeps the thing on straight. 

 

Cheers Paul



#7 BQ Octantis

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Posted 04 July 2022 - 09:31 PM

It's not that I don't have experience with dew (indeed, I was due). One of my first astronomy inventions (shortly after moving to Virginia from Texas) was a dew shield for my Celestron C5 made out of a cross-stitch kit and some duct tape. And I still have my homemade Neoprene + Velcro dew shields for my 10x50 binoculars. But I acquired my Mak 180 while in popcorn fart country 5 years ago, so I'm only now having to deal with it for this setup. Still, I blame the seeing.

 

And it's not that it's a bad image. It's just that I've actually measured the detail limit for this setup. So I'm just polluted with knowledge that clouds my expectation…

 

BQ


Edited by BQ Octantis, 04 July 2022 - 10:30 PM.

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#8 yock1960

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Posted 05 July 2022 - 05:48 AM

It's not that I don't have experience with dew (indeed, I was due). One of my first astronomy inventions (shortly after moving to Virginia from Texas) was a dew shield for my Celestron C5 made out of a cross-stitch kit and some duct tape. And I still have my homemade Neoprene + Velcro dew shields for my 10x50 binoculars. But I acquired my Mak 180 while in popcorn fart country 5 years ago, so I'm only now having to deal with it for this setup. Still, I blame the seeing.

 

And it's not that it's a bad image. It's just that I've actually measured the detail limit for this setup. So I'm just polluted with knowledge that clouds my expectation…

 

BQ

Okay, I give up, 'popcorn fart country'? 

 

Steve



#9 BQ Octantis

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Posted 05 July 2022 - 03:29 PM

Okay, I give up, 'popcorn fart country'?

 

lol.gif

 

I was just responding to Kiwi Paul's line

 

"You’re not in an area where the boundary layer is drier than popcorn fart as in the Outback!"

 

In the US, the phrase drier than a popcorn fart is generally reserved for places west of the Mississippi. See this reference guide of Texasisms under the heading Dry:

 

https://www.texasmon...ake-a-stick-at/

 

Where I lived in the Red Centre is even drier than that: dewless.

 

Cheers,

 

BQ


Edited by BQ Octantis, 05 July 2022 - 03:30 PM.


#10 BQ Octantis

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Posted 05 July 2022 - 03:33 PM

Here is the shot of my telescope with the felt dew shield. As Steve says he and I have it on the telescope pretty well every imaging session. Sometimes dew may form (see signal drop on histogram) but a blow with a hair dryer will clear it quickly and conditions return to settled fairly quickly.

 

As you may guess the front end corrector plate is located about half way up the tube, the rest is protection from dew. Having it fit the telescope so far down keeps the thing on straight.

 

Bloody hell, mate, is that the new rig?! Looks pretty sweet!

 

I just bought the Celestron C6-C8 dew shield…a mere US$35. Hopefully it's long enough.

 

What's the story with those dew heaters? I read they can affect stability, but I may have no other choice for my DSO lenses…

 

BQ



#11 Kiwi Paul

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Posted 06 July 2022 - 02:16 AM

Hi BQ,

 

Yes, that's my long awaited C9.25 SCT with Ioptron CEM40 goto mount. I'm pretty happy with it. There's lots yet I need to learn about the mount and setting up for more wifi control.

 

I don't know whether the electrical dew heaters affect seeing or not. I remember reading on CN how one person uses a fan blowing in the direction of the secondary end of the telescope and then another (Borodog?) who set up an umbrella close by and perhaps had the scope somewhat under it and apparently it worked well?

 

Cheers Paul



#12 matt_astro_tx

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Posted 06 July 2022 - 06:08 AM

Hey it's something.  Good on ya.



#13 BQ Octantis

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Posted 06 July 2022 - 03:43 PM

Hey it's something.  Good on ya.

Ha! Very true. And the ringing out of the workflow for the Northern Hemisphere was incredibly worthwhile. There is no BQ Octantis here (besides me), so sussing out the alternatives was actually kind of fun. Just through the eyepiece on the Mak, I was able to eyeball a ~3' accuracy on the NCP with the nearby asterisms. I might have to write a post about it similar to my post on BQ Octantis.

 

 

…another (Borodog?) who set up an umbrella close by and perhaps had the scope somewhat under it and apparently it worked well?

 

OMG! I was literally putting my accessories on a table with a parasol hole right next to the scope…while the parasol and its base were over in a corner by the house. At 40˚N, the planets are always far from zenith, and that's mainly where the dew comes from. I'm glad you mentioned this on my first dew run rather than 10 years afterward! I'll have to give it a go.

 

Cheers,

 

BQ


Edited by BQ Octantis, 06 July 2022 - 03:43 PM.

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#14 Kiwi Paul

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Posted 06 July 2022 - 09:01 PM

Yes, it’s worth a try. I guess what is happening is that the telescope surfaces are radiating to a bold sky. With the parasol present, this CNN is a warmer surface and thus slows the cooling and thus dew formation.
Cheers Paul

#15 BQ Octantis

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Posted 07 July 2022 - 03:52 PM

Yes, it’s worth a try. I guess what is happening is that the telescope surfaces are radiating to a bold sky. With the parasol present, this CNN is a warmer surface and thus slows the cooling and thus dew formation.
Cheers Paul

I reckoned it would simply block the downward movement of the atmospheric water vapor. But as along as it works!



#16 Kiwi Paul

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Posted 07 July 2022 - 04:57 PM

I should have checked my message: bold = cold and CNN should have been umbrella/parasol. Yes you are right, there is a flux of moisture downward but it’s because of condensation on a surface colder than the dew point of the air.
Cheers Paul

#17 BQ Octantis

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Posted 08 July 2022 - 07:10 PM

Got the dew shield in. Not too happy with it. Looks like I'll have to go the DIY route you did. I might try the Neoprene-Velcro route I used for my binos before I go the glue route. But the wife's hot glue gun is armed and ready.

 

On a happier note, I received the replacement motor controller for my Orion SkyView Pro—so the GoTo is once again functional! laugh.gif  I rehabed the tripod with some grease on the leg screws and some silicone lubricant spray inside the legs. I had already replaced the grease on the gears after the mount weathered a big Outback dust storm, so at this point it's tickety-boo. cool.gif

 

Now I just need another clear morning with no commitments the rest of the day…

 

BQ


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#18 BQ Octantis

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Posted 10 July 2022 - 08:41 PM

I received my roll of 1/8-in (3 mm) neoprene today. I got a strip of 2-in sticky-back velcro and assembled a solution. The result was as good as the set I made for my binoculars (that are still usable after 20 years).

 

Looking at Paul's setup, it looks like he's insulated the whole scope. And reading up on the causes of dew, I'm now wondering where to place the dew shield. My shield is 17-in long. The forward lip of the scope is 2-in; attaching there puts 15-in forward of the scope. I can also slide the shield down to the edge of the dovetail 6-in from the lip, leaving 11-in in front of the scope. If I notch, I could push it down until it gets impeded by the saddle.

 

I'm feeling like the edge of the dovetail is probably the best compromise between hiding the sky and insulating the OTA:

 

scope.jpg

 

BQ


Edited by BQ Octantis, 10 July 2022 - 10:00 PM.

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#19 Kiwi Paul

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Posted 10 July 2022 - 10:03 PM

Hi BQ,
That looks really good. I probably would have used some sort of foam rubber if I had come
across it before the 2mm felt. The only reason I had the felt tube fit all the way down
to the bottom end of the scope was mainly to ensure that the dew shield stays on straight.
It fits like a glove!!
But as you mentioned, it will actually insulate the scope too. I wonder what the upshot
of that is. I'm not sure if it is a benefit or not. I'll have to think about that.
I think the more you have out front of the telescope the better but fitting it back to
the dovetail sounds like a good solution. I'm sure it will improve things immensely.

Cheers Paul

Just an after thought, there have been cold mornings when we have a general frost all
around and where I have seen frost/ice on the felt that fits over the telescope
tube. So it it probably affects the general temperature of the OTA - for good or bad??
I'm not sure.

Edited by Kiwi Paul, 10 July 2022 - 10:06 PM.


#20 BQ Octantis

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Posted 10 July 2022 - 10:10 PM

Hi BQ,
That looks really good. I probably would have used some sort of foam rubber if I had come
across it before the 2mm felt. The only reason I had the felt tube fit all the way down
to the bottom end of the scope was mainly to ensure that the dew shield stays on straight.
It fits like a glove!!
But as you mentioned, it will actually insulate the scope too. I wonder what the upshot
of that is. I'm not sure if it is a benefit or not. I'll have to think about that.
I think the more you have out front of the telescope the better but fitting it back to
the dovetail sounds like a good solution. I'm sure it will improve things immensely.
Cheers Paul

 

Dude (or "dewed"…get it!? lol.gif),

 

The 3mm foam worked great tonight. I, too, found that fitting the shield lower on the OTA gave better alignment between the two. After I put my little one to bed, I did my first GoTo calibration with the new motor control box. It worked like a champ—for the first time in almost two years! laugh.gif  By that point there was already dew on pretty much everything I had out on the patio table. But the Mak's meniscus stayed clear…and get this: the OTA was also dew-free! So I think there's something to the insulating aspect, too.

 

BQ


Edited by BQ Octantis, 10 July 2022 - 10:21 PM.

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#21 Kiwi Paul

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Posted 10 July 2022 - 11:26 PM

That's great. I can appreciate how happy you are with your mount operational again.

I just went for a walk and was thinking about insulating the OTA. I was thinking that without
the insulation, as the surface of the tube cools there would have to be some currents
set up inside the OTA. With the insulation, that cooling would much more muted?? and perhaps
less disturbance to seeing. One could actually investigate this by looking at an out of
focus star to look for said currents with and without the dew shield.

I remember there was some discussion on this a while ago - about insulating the OTA.
Can't remember who that was and i haven't done a search as yet.

Cheers Paul

#22 BQ Octantis

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Posted 11 July 2022 - 04:12 PM

That's great. I can appreciate how happy you are with your mount operational again.

I just went for a walk and was thinking about insulating the OTA. I was thinking that without
the insulation, as the surface of the tube cools there would have to be some currents
set up inside the OTA. With the insulation, that cooling would much more muted?? and perhaps
less disturbance to seeing. One could actually investigate this by looking at an out of
focus star to look for said currents with and without the dew shield.

I remember there was some discussion on this a while ago - about insulating the OTA.
Can't remember who that was and i haven't done a search as yet.

Cheers Paul

Happy as Larry, mate!

 

I was also pondering the currents with and without the shield. But eventually, at a given temperature everything has to hit equilibrium—even with a gradient, no?

 

BQ


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