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Scope maintenance in remote observatory

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#1 physics911

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Posted 19 June 2019 - 11:52 AM

correct me if I'm wrong but it seems most people with remote observatories are leaving the telescope and guide scope uncapped.

If this is correct how are you managing dust accumulation, spiders, insects, etc getting on the lenses?

#2 CharlesW

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Posted 19 June 2019 - 12:22 PM

I live about 150 miles from my scope. I make it a point to visit at least once every six weeks to check up on things but otherwise you can’t worry about it. Flats will take care of the dust. I’ve only ever seen a spider web on the outside structure of the scope and as long as you don’t have any lights on the flying bugs won’t know it’s there.

To keep things in perspective, I took a tour of the facilities at Mt Lemmon, outside of Tucson. Those scopes were covered in ladybugs. I don’t mean a couple, I mean covered.


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#3 physics911

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Posted 19 June 2019 - 12:49 PM

How often are you taking flats? I get to my observatory about every 2 to 3 weeks but wasn't planning on automating The flats process.

#4 petert913

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Posted 19 June 2019 - 12:59 PM

I would get a remotely operated shutter for the front of my main telescope.



#5 Ed Wiley

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Posted 19 June 2019 - 01:29 PM

I had a cover on my SCT in a roll-off roof (2 hours remote). Problem,; open cover acting as a weather vane. I removed it. I clean the corrector plate a couple of times a year, no big deal. Flats: every observing session. But you can check that by flatting the flat you took last week. Does the flattened flat look clean? If so, no worries. If you do this a while you get the idea of how often you need to take flats.

Ed


Edited by Ed Wiley, 19 June 2019 - 01:44 PM.


#6 physics911

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Posted 19 June 2019 - 01:50 PM

I really really do not want to do flats every time if I don't have to. I totally understand the need but I only have a DSL connection there so 100 new flats would take 2 days to upload to home and even remoting in and building my master flats on the observatory computer would be slow.

#7 Sixburg

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Posted 19 June 2019 - 01:58 PM

A hundred flats?!? Regarding the main question we have quite a few scopes installed. Some with covers (most often flip flats) and some with built in mirror covers.

In my experience dust happens, but is way over-rated in terms of impact on images and equipment. Of course there is a limit, but our scope are cleaned annually at most ;-)

Some designs are more prone to dust, but generally it’s not a huge concern (of ours and we run all common optical designs)

#8 physics911

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Posted 19 June 2019 - 02:04 PM

100 flats equals 25 each for LRGB or 75 equals 25 each for HA, O3, S2.

I guess my short answer is get my roof automated leave the caps off and see where I stand after taking some pictures. or I guess I don't even have to wait to automate my roof. I can just leave the caps off next time I go up there and then check it the time after that. And I'm not opposed to cleaning my optics once or twice a year

#9 CharlesW

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Posted 19 June 2019 - 03:00 PM

Your real question should have been, how do I transfer the data that I’ll collect since I have DSL? You need to remember that a 3 second flat has as much data as a 30 minute sub. And, unless you’ve got a way to run your flats with the roof closed, you can’t get 75 flats a day much less 100. It’s impossible. Might take three, cloudless days, to get that many. Maybe take flats every two weeks? And 100 flats = 1.6 gigs. Zipped you are probably still looking at 1 gig?  

 

I dont know know what you pay for your DSL plan but you should consider Excede satellite. Should be about $70 a month for the speeds and data that you’ll need. Or, you don’t try and transfer the data at all. Store it on an external drive and wait till you drive to your obs to collect it. I may come into possession of a 50 mb camera and I’m probably not going to be able to transfer all that data unless I’m extremely diligent and do it everyday, and twice on Sunday.



#10 physics911

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Posted 19 June 2019 - 05:19 PM

Bandwidth limitation is only a side effect of my original question.  

Since I'm up there every 2 or 3 weeks, it really isn't that big of a deal to wait to get my data on a thumb drive if I have to.

To bring it back to my original question, I'm really just trying to understand how others manage their system in a remote location.  

I think my best plan of action is to try it without caps to start with and see what the process feels like over a month or two.

If that turns into too much dust on the lens, dew spots, bugs, etc., then I will either buy a flip flap, or build my own. 

I already have a SmartThings system in my observatory, so it wouldn't be too big of a stretch to setup an actuator like a flip flap which would automatically close at sunrise. 



#11 Raginar

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Posted 19 June 2019 - 08:42 PM

They make automated dust covers. I think most of us just let it accumulate. It doesn’t really affect the image as long as you’re taking flats.

#12 CharlesW

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Posted 19 June 2019 - 09:40 PM

Keep in mind that just because the sun goes down doesn’t mean there isn’t dust falling on your vertically pointed glass. If you can’t keep the dust off at 1:30am, why worry about it when the roof is closed and the scope is lying horizontally and the dust is just falling on the tube? You are certainly free to do whatever you want to do and spend money as you see fit but sometimes we fret over things without stepping back to look at the whole picture. 


Edited by CharlesW, 19 June 2019 - 09:41 PM.


#13 physics911

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Posted 20 June 2019 - 07:11 AM

I'm not fretting. I'm just reaching out to a knowledgeable community for their experience.

you are of course right about there being dust all the time. However, there are some significant differences between day and night. anytime I'm imaging my dew heater is almost always on so I won't get dew spots on the lens. This won't be true if I leave it without a cap at night when I'm not imaging. also my observatory is at our cabin we go to on weekends. That means during the day I'm mowing the yard and driving up and down a very dusty dirt road and other things like that does stir up a lot of extra dust. when I automate my roof later this summer I'm going to take that opportunity to make my observatory a lot more dust proof but I don't think it will ever be completely sealed against a daytime environment.

again, my purpose of this thread is to get advice and talk out ideas from people who have done this before.

#14 Ed Wiley

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Posted 20 June 2019 - 08:33 AM

My observing program is simple: differential photometry with BVIc filters. Further, I do not need or want a large sensor (mine is a 1603-based camera). So, taking flats frequently with a spike-a-flat is no big deal (20x3 = 60 flats), I simply use TeamViewer for transfer during the day.  (I also have DSL.) So, I am not facing the problem of a multitude of flats. However, if I was taking flats for AP with a bunch of filters, much would depend on my OTA/camera set-up. Most (all?) the the dust bunnies, etc. that affect an image come from the filters and optical window of the camera. A speck of dirt or piece of pollen on the mirrors (or objective lens or corrector lens) casts such huge shadow that the shadow is are larger than the sensor. So when I clean my corrector plate on my C11 Edge, it is for light transmission, not to get rid of dust bunnies.

 

That said, I have already given my strategy for determining how often to take your flats. I think it is valid. Tonight take a series of flats with, say, you green filter. Make a master (correctly calibrated with flat darks and/or bias). Repeat this in a week (or a day or a month if you wish). Divide the flat of last week by the flat of this week. If you see any artifacts, then this indicates that you need to take flats more frequently as you have accumulated stuff on your filters and optical window during that period of time. Do that from time-to-time with all your filters as a check. When you see what you think is a significant change on one filter, you might suspect other filters are also compromised. Then take a bunch of flats.

 

If you are interested in where the dust bunnies reside, download: 

https://www.ccdware....ources/dust.cfm

 

Ed


Edited by Ed Wiley, 20 June 2019 - 09:43 AM.


#15 Dan Crowson

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Posted 20 June 2019 - 08:54 AM

I'd start this out with people's results will vary.
 
I have a truss tube RC scope located in a ROR in southwest New Mexico. I share a building with two other people. My scope does not have a shroud but my camera does have a shutter. It can be windy and definitely dusty and we open if the wind is gusting less than 15 MPH.
 
I've found that dust isn't that big of an issue. I do have a flat panel but I can usually go months on a set of flats. At times I could get something blown into the camera but it is rare. Things do get dusty on the tube but the mirror is decent after three plus years of use - every clear night of the year. My partner's DK has not been cleaned since install as well.
 
As long as you're ok with dust collecting on the mount and everything else, you'll be ok. If using a refractor, I might think about some kind of flip-flat like device (buy or make) but even without one, dust is much of a non-issue.

Dan



#16 StarmanDan

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Posted 20 June 2019 - 09:32 AM

So when a clean my corrector plate on my C11 Edge, it is for light transmission, not to get rid of dust bunnies.

 

 

Ed

My club has a "remote" observatory with a 24" RC.  While our scope has mirror covers, it doesn't completely cover the mirrors as the mirror cage is open to the air even with the covers closed.  So we get quite a lot of dust.  Like Ed, our scope is mostly used for photometry.  We do flats every time we observe because the scope may not get used for months at a time.  We only clean the mirrors about once a year for the same reason as Ed.  Between cleanings, we may get a loss of about 1 magnitude with a 30 sec image.  




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