Barn door tracker

[JamesF]

I was working on the basis of "1 pixel trailing in an hour long sub at 50mm with my 1100D".

Pixel size is 5.2um, so if I've done the maths right, one pixel is 206265/50*0.0052 = 21.45 arcseconds per hour.

James

[Ags]

Yeah I know.... I'm just trying to get the software perfect. Even if you had that kind of tracking, polar alignment would probably be off, and atmospheric refraction would throw in a spanner too.

EDIT: I think my errors are coming in from trying to keep the clock face and the absolute angle in synch. When I rewrite the software to drive a stepper I won't have to worry about that.

[JamesF]

I know what you mean, Agnes

I've been beating my head against a user-space driver I've written for my image capture application for the QHY5L-II camera for a week or so.  There's no documentation other than QHY's open source driver that appears to be inconsistent, buggy and, in places, just plain weird, and a kernel-space driver for a completely different camera based on the same sensor.  What I've got works pretty much ok, but because there's no real reference documentation it's far from perfect and that's quite irritating.

James

[Ags]

Programming always reminds me I'm not the sharpest brick in the woodpile... :-)

[MyRomeo]

Hey, great thread, I do like to see everyones take on barn door mounts! Heres a shameless link to my current project which I must get out in the field!

http://stargazerslounge.com/topic/201484-3d-printed-motorised-barn-door/

I'm not aiming for quite such long exposures as yourself as the light pollution in my area limits me to minutes at a time!

[Ags]

Looks good! Are those 3D printers smelly?

[MyRomeo]

What a strange question...

Yes, actually, if you sniff real close you can smell the plastic ever so slightly. Certainly not much tho

Sent from my iPad using Tapatalk

[Ags]

Ah, I thought they would smell like a chem lab.

[JamesF]

You sound almost disappointed

James

[happy-kat]

That mini printer is fascinating but I don't need one! :-)

[Viewmaster]

For maximum exposure times with long focal lenses avoid hinges like the plague.

I replaced all mine with ground steel shafts and ball races on both moving platforms on my type 3 tracker.

Also ball races noiw fitted on the stepper motor and drive nut gimbols.

You can see the two steel shafts with their bearings in this piccy.

Now being tested out.......when the clouds go.

DSCF1230 by [url=http://www.flickr.com/people/43238397@N06/]

[Ags]

If NASA built barn doors...

[Viewmaster]

If NASA built barn doors...

One of NASA's astronauts  did on the ISS............

http://en.wikipedia.org/wiki/Barn_door_tracker

[Ags]

Silly fellow... He's trying to do AP indoors:

[MyRomeo]

Viewmaster, my first version used hinges and it was able to shoot 10 minutes with even the most basic of alignments however for the 3d printed model I have used four bearings and a fixed shaft. It's very stable, even really pulling on the parts shows no sign of play. If I disengage the drive end the bearings allow the whole thing to rotate very smoothly.

I should be out testing it right now but I'm stuck waiting for a phone call

[Ags]

Slightly OT, but anyway, I just found this site - good price for astro mod plus cooling (the astronaut above is one of their customers):

http://www.spencerscamera.com/store/store_product_detail.cfm?Product_ID=15&Category_ID=1&Sub_Category_ID=2

[Ags]

I had what you might call a first light with my manual barn door and android app tonight. I took a widefield of Jupiter and some nearby clusters, amassing 12x90s subs. I didn't expect too much so I didn't shoot flats or darks. I collected the subs in bursts of 3 at a time, using my app's Rest button to rest in-between each burst for a couple of cycles (when you take a rest you just quickly dial a couple of turns ahead, and it beeps when the stars have caught up with you and you need to start cranking again).

First, here are the obligatory no-tracking and with tracking demos (50mm, 90s, crop camera):

And here is my little composition of Jupiter and clusters:

(By the way, the gradient in the image was removed with my home-made gradient extractor)

[catman161]

Nice shots Home made gradient extractor sounds interesting-care to elaborate?

Sent from my iPhone using Tapatalk

[Ags]

Its written in Java. I blur the image slightly, divide the image up into tiles, and then find the darkest patch in each tile. Then I make a gradient based on interpolating those minima and then subtract it from the original image. The code is a total mess however...

[happy-kat]

Look at all those stars and neat too, that cluster you got top right if earlier might be M44?

The rest you mention is that when you have closed the shutter adn are waiting to open it again?

[Ags]

I did 3 90s subs back to back, then rested 2 minutes, but dialed ahead two minutes at the beginning of each rest period so that the image wouldn't drift.

I wasn't expecting the cluster, so I think it must be the Spanish Inquisition! :-) I am waiting for Astrometry.net to tell me what it is. Maybe M35?

[happy-kat]

I understand the rest now and dialing ahead, but why not just take another 3 subs without resting?

[Ags]

I find it difficult to crank continuously, I need a bit of a break now and then. My arm gets tired and my concentration falters if I go on too long.

[Ptarmigan]

Its written in Java. I blur the image slightly, divide the image up into tiles, and then find the darkest patch in each tile. Then I make a gradient based on interpolating those minima and then subtract it from the original image. The code is a total mess however...

Interesting idea.

In the limit (of tile size) does this equate to a digital high pass filter ?

[Ags]

I guess you could say so. The gradient extractor has the behavior of deleting DSOs if they are larger than the tile size! I need to write a GUI so I can disable DSO tiles, but with my rudimentary AP equipment I only shoot really widefield stuff so it's not a big problem for me.

Back to cameras and lenses - I also shot a few tests at 100mm and these did not go so good... My 4 minute test shot was passable, but I did several 90s subs and they were all write-offs.

On a mechanical level I had some stiffness in the bolt turning tonight. As happy-kat suggested, my bolt handle is too short. Also, i'm sure some oil would help a lot.