furrysocks2

Hi @AKB.

Unfortunately, I never really got round to having a proper try out. I had hoped to, but I broke my go-to mount and then stopped much astro at all.

Have you experimented much in this past month?

Matt

If not, it might be possible to 3D print a replacement. The link below won't necessarily be the right part and there may not be a model already for the cog you need, but it proves the point.

https://www.thingiverse.com/thing:1761570/comments

The hard bit would be 3D modelling what you need, anyone with a printer could then print a few for you.

Another little treat, Sir J. F. W. Herschel's observation of "Mr. Sixth"... (May 4th, 1837)

https://babel.hathitrust.org/cgi/pt?id=wu.89080139876&view=1up&seq=312

Shame the 12" mirror set never saw light, but for the sake of fitting it all to the length of the light path, as you say better to do it properly from the start.

Good luck!

Matt

You can appear to get a signal dead-center in the band you're looking at, but I though "Correct IQ" got rid of it, not sure. It may well be that there is no station being broadcast on 98.3 within range of where you are now. Zoom out with the slider top right and perhaps play with AGC/gain in the configuration dialog and see if there's anything visible then.

I happened across https://www.hathitrust.org/ and searched for items in the catalog containing the word "astronomy".

https://catalog.hathitrust.org/Search/Home?type[]=all&lookfor[]=astronomy&ft=ft

I have spent the last hour or so enjoying portions of https://babel.hathitrust.org/cgi/pt?id=nyp.33433090906904

Introduction to practical astronomy, 1841. Author: Mason, Ebenezer Porter, 1819-1840.

There appear to be articles dating back to the early 1700s. Other sites such as this exist, I thought this may be of interest to someone.

Great result! Well done.

Lovely pictures!

I'd never seen them before, but I was standing out back in my underwear at midnight last night marvelling at the same phenomenon, when my wife returned from a nearby hostelry. She already knows I'm pretty weird.

2 hours ago, happy-kat said:

what did you use to create your graphs please? That's a busy constellation. Your camera and lens must be super light on your mount.

The graphs are on the "Drift Graph" tab in SharpCap's live stacking.

Pretty minimalist set up, yes!

Followed by a comparatively quick 50@5s, gain 50 on the Perseus cluster.

Tonight has been my very first go with an AltAz GOTO mount. I've got my Datyson T7M (ASI120MM) with a 50mm f/1.4 CCTV lens mounted to a couple of 3D printed parts, one of which was a repair to the mount so that I could actually do this. I'm sitting in the warmth, drinking herbal tea.

I took a couple of darks for different exposure/gain settings and shot a few targets but ended up selecting M52 for the rich star field in the rest of the frame.

Field of view is 5.82 x 4.36 deg at 16.4 arcsec/pixel. 100@32s at gain 2.

Field rotation is obvious over nearly an hour. Don't know if I got focus spot on or not, and 30s might be starting to push it.

To try this out, I've integrated with SharpCap through a bit of scripting and a DLL (https://forums.sharpcap.co.uk/viewtopic.php?f=14&t=1141 for details).

1 hour ago, Timebandit said:

Nice  Truss design?

Have you future proofed the scope?

I am sure you could get a lot bigger primary mirror in the lower cradle section.

Maybe time to start a 18" grind ?

That's not my scope, unfortunately.

http://members.ziggo.nl/jhm.vangastel/Astronomy/30cmscope/5_30cm.htm

Have you got a design in mind already?

I've got a 12" f/5 revelation dob and unless I sell it, hoping to re-mount the mirrors as a lighter-weight collapsible dob. I think I've settled on a design where the struts are attached directly to the altitude bearings. I like the relative simplicity and wider base for the struts which should (I guess) increase stability of the top end.

A stunning fit and finish to your observatory, congratulations!

The photographic results you get and post here are most enviable and like the descriptions you post alongside, this video really highlights your passion for astronomy. A wonderfully communicative short film.

Valeu!

Here's my first wide-ish-field effort... 16.4 arcsec/pixel, 5.5x4 degrees roughly - had to crop out the drift. I'm down to mag 13 I think.

Exposure set to 2.5s, gain to 75%, average of 20 darks subtracted in SharpCap, 100 frames captured, 50 stacked in DSS, curve and crop in GIMP.

Taken using a Datyson T7M (ASI120MM clone) with a 50mm focal length f/1.4 CCTV lens, wide open, zip tied to a pistol-grip tripod head with some pluck-foam padding, bolted to a board of wood, three screws sticking out the bottom for feet.

Lucky me to catch M42 in Orion last night... iPhone through 16mm on a 12".

I'm not versed in such things at all, but thinking what this means in practical terms for me...

I have just read that the linear size of the airy disc depends only on the focal ratio (0.00124 mm times the focal ratio). Also that the angular size of the airy disc is 260/diameter mm (http://www.bbastrodesigns.com/AiryDisk.html). I don't know if that's accurate to begin with but I wanted to try and work through the above in terms of what that might mean for the two scopes and one of the cameras that I own.

For example, my 12" 1520mm (f/5-ish) - I calculate airy disc as 0.0062 mm, 0.85". I've seen a theoretical resolving power value of 0.38", which is approximately half of that value.

4.8 pixels per airy disc would imply a linear pixel size of 6.2um/4.8 = 1.3um, or an angular pixel scale of 0.85"/4.8 = 0.175 arcsec/pix.

My camera, Datyson T7M, has 3.75um pixels, or 1.65pp. A 2x barlow takes me to 3.31pp, and a 3x barlow to 4.96pp. Suggesting perhaps a 3x barlow.

For my scope and camera (1520mm, 3.75um), I get a natural pixel scale of 0.51 arcsec/pix, x2 barlow to 0.25 arcsec/pix or x3 barlow to 0.17 arcsec/pix.

For my DIY scope, 215mm 1635mm, f/7.6-ish...

AiryDisk - 0.0094mm, 1.209". 4.8pp implies 1.96um or 0.25".

Same camera, 2x barlow, 5.01pp or 0.237 arcsec/pix.

So using the Datyson T7M camera in my f/5 12", I should use a 3x barlow and if I were to keep my 8.5" f/7.6, a 2x barlow.

Is this how I should be going about applying what you've written above? I've not taken into account any central obstruction, and I seem to be rather oversampling (though I've read that's "good" for planets). Is the fact that both of these end up around f/15 just a coincidence? At 0.17 arcsec/pix for the 12", I get a field of view of 3.6' x 2.7' - that might be fun centering Jupiter.

Or am I misunderstanding this completely?

34 minutes ago, JOC said:

furrysocks2 - I think that is an excellent effort - nearly as many as I have!  Well done!

There's more...

• 11mm 80degree, another ebay mistake (although interesting to try it in the 12" before I stamp on it)
• two 25mm supplied-with-2nd-hand-scope EPs.

I think that brings us even in number (excluding my box set), but certainly not in average quality.

Edit... no actually, I've got a 3" blue penguin scope with the set of all three helical EPs.

The case at the top doesn't really count... that came with the 12" scope I got the other day.

In the bottom row, I'm afraid I do have a pair... :/

Left to right

• crappy 40mm plossl
• SW Aero ED 35mm
• Vixen NPL 30mm
• Andromeda Flat field 19mm
• Lightwave 12.5mm LER
• Vixen NPL 8mm
• TMB II 6mm

The Vixen NPLs were the two EPs I bought to replace stock on my 76mm Aldi/NatGeo newt - I loved them in that! Most satisfying view of the Double Cluster I've ever had was through that 30, scope balance on a park bin at a star party. The 40mm plossl was a cheap ebay mistake, AFOV must be 40 deg or something. And I never really got on with the TMB 6mm in my 8.5" f/7.6 - 272x on Jupiter was a bit much, but actually tonight in the 12", that 6mm took me to a hair over 250x on the moon which was probably just at the limit that seeing would support, but I got it focused and enjoyed the view, if a little tetchy, narrow and fleeting. The Aero 35mm, 19mm and 12.5 Lightwave were all more recent SGL purchases in the last year or so. I like the three of them.

Coming to join them soon is a 16mm 82deg Nirvana.

49 minutes ago, JOC said:

I wonder whether anyone else has such a mismatched collection?

You are not alone.

I learned on a grant, first paid flight was my first solo. Maybe only a couple of dozen flights since then. Wish I could afford to get back into it now.

Slightly more modest, my last solo flight was in this:

1 hour ago, Stub Mandrel said:

(I usually use AVR Assembler)

We AVR going a PIC off-topic....

(Edit: The day I met my wife, I had just used assembly and interrupts to get an LED flashing on a PIC)

2 minutes ago, rotatux said:

Beware that if you use a fixed delay in the sleep, this kind of loop has inherent timeshifting builtin because of various lags in execution.

Unless it's already the case, you should aim for fixed average frequency, by using the builtin clock to compute the next delay each cycle. I mean something like:

avgPeriod = CONSTANT
target = clock() + avgPeriod
while (tracking) :
	step()
	sleep(target - clock())
	target += avgPeriod

 

Sweet, yeah precisely. I think it's the additional latency/imprecision that means it works better for the moon than for the background.

In terms of things to be getting on with, it's definitely "mount first". Clear tonight, but no time to spend today. :/