Imaging on grass
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Tom Blahovici
Being in Canada, last night would have been a good night to take this literally....However...
Last night I tried out my portable "wheely bar" setup for my FSQ106 and AP600 GTO mount. I used 1 foot by 1 foot, 2 inch thick concrete blocks under the leveling screws and did a polar alignment with the polar scope in the AP600. My first image, 30 minutes O3 on NGC7000 was amazing. The tracking, was 0.25" with pretty well no corrections at all. Granted the seeing was really special last night, very rare. My imaging uses Voyager and I typically focus each 30 minutes where the scope does a goto to a nearby star in the Voyager database and then continues imaging. After the first image I started to get large gradual swings in the dec and RA, up to 4" of arc errors after which Voyager would abort and start over. After two or so tries I then managed to get another nice sub. Likewise for the third sub. After this, I was no longer really successful. So I took a look at the polar alignment through the polar scope and polaris had moved quite a lot. Probably a good 1/8 to 1/4 of the field of view. So my thinking is that as the night progressed, and the scope changed position, the blocks started to shift. This happened during the exposures. So, how do you image on grass? Is 30 minute subs out of the question? Do you polar align frequently? Thanks for any insight. Tom
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ap@CaptivePhotons.com
I dug holes, filled with sand, packed, put in gravel and packed it, and put pavers down in three spots at grade level (so the landscapers can just move over them). That way the foundation doesn’t have to be taken up and put back, so any settling happens and mostly stops.
Obviously ground conditions and climate (rain and/or freezing) may still be an issue, but the better bed under the pavers the more stable they will be.
Main downside is it makes it hard to pick your spot for wind.
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davidcfinch9
Where did you get the “wheely bar” or did you custom make it? David
From: main@ap-gto.groups.io <main@ap-gto.groups.io> On Behalf Of ap@...
Sent: Sunday, July 11, 2021 1:10 PM To: main@ap-gto.groups.io Subject: Re: [ap-gto] Imaging on grass
I dug holes, filled with sand, packed, put in gravel and packed it, and put pavers down in three spots at grade level (so the landscapers can just move over them). That way the foundation doesn’t have to be taken up and put back, so any settling happens and mostly stops.
Obviously ground conditions and climate (rain and/or freezing) may still be an issue, but the better bed under the pavers the more stable they will be.
Main downside is it makes it hard to pick your spot for wind.
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When I lived up in Alaska I put a steel pier into the ground and set it with concrete. I took rhe scope and mount off of the pier when I wasn't using it and put a rubber canvas kayak bag over the pier. When I moved from Alaska to Hawaii, I made a plant hanger head for the steel pier. Worked great.
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Worsel
David
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Hi Tom I'm in Calgary and image on grass as well with my AP900GOTO and a Televue NP127is on an AP portable pier. I tried cement blocks as well but found they move too much as the weight of my rig compresses the grass under the blocks. I have since gone to three steel plates with two 8" pieces of rebar rod welded to the bottom of each plate. I pound these into the ground and leave them there. As the grass dies under them, they sink down to the dirt and are reasonably, but not totally, stable. I minimize movement by setting up my rig several hours before imaging which gives the plates a chance to settle in a stable position. This works ok since I image at between 525 and 660mm f/l. This wouldn't be very satisfactory at longer f/l. My next thought is to set up a permanent pier to which I would install my rig every time I image or drill three 6" holes 4' deep and pour concrete pads level with the ground. Hope this helps. Attached is a pic of my setup. Don Anderson
On Sunday, July 11, 2021, 11:01:26 a.m. MDT, Tom Blahovici <tom.va2fsq@...> wrote:
Being in Canada, last night would have been a good night to take this literally....However... Last night I tried out my portable "wheely bar" setup for my FSQ106 and AP600 GTO mount. I used 1 foot by 1 foot, 2 inch thick concrete blocks under the leveling screws and did a polar alignment with the polar scope in the AP600. My first image, 30 minutes O3 on NGC7000 was amazing. The tracking, was 0.25" with pretty well no corrections at all. Granted the seeing was really special last night, very rare. My imaging uses Voyager and I typically focus each 30 minutes where the scope does a goto to a nearby star in the Voyager database and then continues imaging. After the first image I started to get large gradual swings in the dec and RA, up to 4" of arc errors after which Voyager would abort and start over. After two or so tries I then managed to get another nice sub. Likewise for the third sub. After this, I was no longer really successful. So I took a look at the polar alignment through the polar scope and polaris had moved quite a lot. Probably a good 1/8 to 1/4 of the field of view. So my thinking is that as the night progressed, and the scope changed position, the blocks started to shift. This happened during the exposures. So, how do you image on grass? Is 30 minute subs out of the question? Do you polar align frequently? Thanks for any insight. Tom
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Tom Blahovici
The "wheely bar" is custom made by myself. This was the first time using it.
In my case, the wife won't allow any permanent pads unless they are just a couple of inches in diameter. Which I guess is a possibility. Tom
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Dale Ghent
How bad this gets for any one person depends on ther soil type and moisture and all that. I use pavers sunk into the ground but major shifts aren't really anything noticeable with my clay soils. I'll start the evening guiding around 0.3" and it'll get to about 0.4 or 0.5". I'll touch up the PA every night, though. It's usually off by around 5-10" over the course of a day or two. I PA using sharpcap through my main camera.
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On Jul 11, 2021, at 13:01, Tom Blahovici <tom.va2fsq@...> wrote:
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Harley Davidson
That's a fine job on the wheely bar Tom! Beautiful workmanship.
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tony On 7/11/2021 4:16 PM, Tom Blahovici
wrote:
The "wheely bar" is custom made by myself. This was the first time using it.
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ap@CaptivePhotons.com
I expect my HOA is more picky than you wife (if not, well, my sympathies). Put in the pavers with a really good foundation, then let the grass grow for a while. They are not very visible, in fact from the side they are not visible at all except right after mowing.
Bigger pavers are probably better but it is more about how deeply you build a good foundation that is not affected by moisture. I don’t have to contend with freeze/thaw, I expect that might be difficult to reasonably counter. But just moisture (which I have in abundance) is handled by a lot of gravel and sand (remember you can make the gravel/sand bed wider than the paver and grass covers it, if you haver it a few inches down).
In my case the holes accept the spikes and self center; I can set the whole thing up night to night and before I polar align I am usually within a few arc minutes just from repeatable placement (I do not remove the mount from the tripod, just the OTA, and weights, then move it on a handtruck). But cranking down a lift should work the same way.
Linwood
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fl.lusen
Tom,
Where is the photo of your wheelie bar. I didn't see it.
Fred
-----Original Message-----
From: Harley Davidson <astrocnc@...> To: main@ap-gto.groups.io Sent: Sun, Jul 11, 2021 4:50 pm Subject: Re: [ap-gto] Imaging on grass
That's a fine job on the wheely bar Tom! Beautiful workmanship.
tony On 7/11/2021 4:16 PM, Tom Blahovici
wrote:
The "wheely bar" is custom made by myself. This was the first time
using it.
In my case, the wife won't allow any permanent pads unless they are just a couple of inches in diameter. Which I guess is a possibility. Tom
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Tom Blahovici
First post
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fl.lusen
Tom,
I apparently never got that one. Can you send me the photo? I am currently configuring a wheelie bar for my 1100 and would like to see what you have done.
Fred
-----Original Message-----
From: Tom Blahovici <tom.va2fsq@...> To: main@ap-gto.groups.io Sent: Mon, Jul 12, 2021 1:03 pm Subject: Re: [ap-gto] Imaging on grass First post
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fl.lusen
Tom,
I was finally able to locate it. Nice job. Did you form the tire mounts yourself or obtain them already bent for the tires?
Fred
-----Original Message-----
From: Tom Blahovici <tom.va2fsq@...> To: main@ap-gto.groups.io Sent: Mon, Jul 12, 2021 1:03 pm Subject: Re: [ap-gto] Imaging on grass First post
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dvjbaja
You know when I first read the subject line of this post, I thought this was about smoking the "devils lettuce" while imaging. Guess I was mistaken. ;-? jg
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On Monday, July 12, 2021, 3:05 PM, dvjbaja <jpgleasonid@...> wrote:
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Tom Blahovici
I bought a set of 4 wheels from amazon. 10 inch. Two of them are pivoting. The set was around $100 canadian.
Tom
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fl.lusen
Tom,
I was referring to the bracket that holds the axel. Did you fabricate that or purchase them?
Fred
From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of Tom Blahovici
I bought a set of 4 wheels from amazon. 10 inch. Two of them are pivoting. The set was around $100 canadian. _._,_._,_ Groups.io Links: You receive all messages sent to this group. View/Reply Online (#79420) | Reply To Group | Reply To Sender | Mute This Topic | New Topic __,_._,_
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Tom Blahovici
Hi, they came with the wheels.
Price has doubled since the spring! https://www.ebay.com/itm/291892581564?hash=item43f62754bc:g:Rz8AAOSwWxNY1BLW
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fl.lusen
Thanks Tom, that helps a lot.
Again, you did a nice job.
Fred
From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of Tom Blahovici
Hi, they came with the wheels. _._,_._,_ Groups.io Links: You receive all messages sent to this group. View/Reply Online (#79424) | Reply To Group | Reply To Sender | Mute This Topic | New Topic __,_._,_
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