Updates to PicGoto Veroboard Layouts for Voltage Control

27 Mar 2014.  I realized I have not posted my updated Veroboard layouts for the PicGoto Simplificado that go with the voltage controller (see this post for layouts), so here they are.

This is the solder side, showing the trace cuts.










This is the component side.  The positive input of the voltage control board connects (through a 100 ohm resistor to pin 9 of the 16F628A) to the "V Ctrl" pin on the bottom trace, and the negative input connects to the ground pin next to the LED (and I guess I haven't actually shown that pin, but you can see a bunch of places you could put it-any of the grounded traces would work).

2 Flips = No Flip, Duh!

25 Mar 2014.  I had another nice night, so I took another image, this time of NGC 3184, the Little Pinwheel Galaxy, which was a new target for me.  I’m a little surprised I hadn’t tried this one before, because it is easy to find, even with just a Telrad; it sits right next to µ UMa, which is pretty easily visible from my back yard (but I’m routinely using the PicGoto to find everything now).  I did use µ UMa as my sync star.  I had an unusual number of satellite trails early in this session.  One nice thing is that I’m getting good enough guiding now that I’m not afraid to use longer subframes.  I could see the surface brightness of this target was low, so I decided to use 600-sec subframes and they worked fine (or at least they did until the breeze started gusting a bit).  The other nice thing about the PicGoto is that it makes doing meridian flips easy (I guess I’ve commented on that before, but it is such a contrast with doing it the old way “by hand” that it just seems remarkable to me).  I’ve been having trouble with PHD2’s guiding calibration after the meridian flip; PHD2 has an option to flip the coordinates, but it always seemed to come out backward anyway.  Then I realized I was flipping them in the PicGoto software (via the “invert” check box) and in PHD2 too.  Two flips = no flip!  Duh!

Date: 24 Mar 2014
Subject: NGC 3184, Little Pinwheel Galaxy 
Scope: AT8IN + HPS Coma Corrector
Filter: None
Mount: CG-5 (Synta motors, PicGoto Simplificado)
Guiding: 9x50 Finder/Guider + DSI Ic + PHD 2.2.2 (Win 7 ASCOM)
Camera: DSI IIc no chiller T = 9 °C)
Acquisition: Nebulosity 3.2.0, no dither
Exposure: 26 x 600 s
Stacking: Neb 3, bad pixel map, bias included, normalize first, trans+rot align, 1.75 SD stack.

Processing: StarTools 1.3.5.279 Crop; Wipe 82%; Develop 87.49%; Contrast; HDR:Optimize; Sharpen; Deconvolute 2.2; Color (Scientific) sat. 275%; Life:Isolate, mask fuzz 24.7; HDR:Equalize; Life:Optimize; Track read noise compensation 75.98%;.  CS6 Astronomy Tools increase star color; Levels; Space noise reduction; Deep space noise reduction; Astro Frame.

A New Target and an Old Friend

24 Mar 2014.  I took advantage of the nice conjunction between beautifully clear skies and a Saturday when I could stay up late this past weekend to image a new, difficult target and to return to my all-time favorite astroimaging subject.  

I found the Medusa Nebula from Beta Canis Minoris using the PicGoto.  This is one of the dimmest targets I have ever attempted; in fact, it is one of those you are not supposed to try with a one-shot color camera from the suburbs, so I was happy to get anything.  I think images with a lot of detail in the nebula would need to be LRGB or narrowband.  Conditions were excellent: cold, clear, and little wind (some came up later in the session).  Guiding performance was very good, but not so great that I didn’t apply some corrections in post-processing (StarTools’ Repair:Warp tool works well).  The technique of using HDR twice in StarTools seems to really help in bringing up faint stuff. 

Conditions were exceptionally clear, so even though I was sleepy I couldn't pass up the chance to image my favorite target, M51 (the Whirlpool Galaxy), once again (and this time without the filter; see my last post to see what a big difference the filter makes)).  There was a bit of gusty wind so I threw out about 1/3 to 1/2 of my subframes.  I imaged up to the meridian, then used the PicGoto again to reacquire the target after the meridian flip.  This is so much easier than doing it "by hand!"  After the meridian flip, I went to bed and let the camera run until daylight.  I think this is my best image of M51 so far (I’m including one of my earliest images for comparison; it’s fun to see how far I have come).  I like the way the tidal streams show up in the new image.  I’d like to understand better the physics of galactic collisions like the one happening in this picture; as the tidal streams show, the collision has flung stars all over.  So here's what I can do with M51 with my current skill set:

Date: 22 Mar 2014

Subject: M51, Whirlpool Galaxy

Scope: AT8IN + HPS Coma Corrector

Filter: None

Mount: CG-5 (Synta motors+PicGoto Simplificado)

Guiding: 9x50 Finder/Guider + DSI Ic + PHD 2.2.2 (Win ASCOM)

Camera: DSI IIc (no chiller, T = 3 °C)

Acquisition: Nebulosity 3.2.0, no dither

Exposure: 23x480 s

Stacking: Neb 3, bad pixel map, bias included, normalize first, trans+rot align, 1.5 SD stack.

Processing: StarTools 1.3.5.279 Crop; Wipe 80%; Develop 87.49%; Contrast; HDR:optimize; Sharpen; Deconvolute 3.0; Color:Scientific 301%; Life:Isolate; HDR:Equalize; Track:Read Noise 7.6%; Magic:shrink 1 pix. CS6 Astronomy Tools increase star color; space noise reduction; AstroFrame

And here's what it was like 3 years ago (and I remember I was thrilled to get this picture!):

One of my earliest (11 Feb 2011) M51 images.  Stack of 33 JPEGs (Keith’s Image Stacker; DSS would not stack these).  Afocal, PowerShot A560 at f/2.6 on camera, 800 ISO, 32 s exposures, U19 eyepiece (system f/2.4).  Processing with GimpShop Curves & Levels.  The spiral arm structure is visible all the way out to the interacting NGC 5195 satellite.

Using the Wrong Filter Hurts!

20 Mar 2014.  Just a quick note to say that the PicGoto Group has come through once again.  My question about hooking up the voltage control board was answered, and I had indeed done it incorrectly.  I just needed to connect pin 9 of the 16F628A chip through a 100 ohm resistor to the input of the LM317 voltage control circuit, and presto, everything works as desired including the LED coming on when it is supposed to.  I used the system to image last night and got decent guiding performance despite light gusty winds.  Unfortunately the image (of M51) turned out terrible because I left my UHC-S filter on my camera (I had intended to image the Medusa Nebula, but couldn’t find it because it isn’t in my Cartes du Ciel database and I was in a hurry; the filter would have been good for that nebula, but it is terrible for M51).  Now I just want to find out if I can really do periodic error correction with the PicGoto.  Even if I can’t, I’ve come out way ahead with this project.  

The UHC-S filter blocks the wrong colors for this target, so I just didn't get enough light despite using 600-sec subframes.

Quality-sorted Stacking is Better

19 Mar 2014.  I’ve been playing with the image of M3 I took last week, trying to improve on the stacking.  By way of review, this was 300 30-sec subframes, and originally I stacked them in Nebulosity 3.2 and used all of them.  I knew this included some bad subframes, and just figured that standard deviation clipping would get rid of the bad data.  While I’m sure that did help, I decided to do a little filtering.  I like the quality sorting algorithms in Deep Sky Stacker, and although I have not used DSS much lately, I decided to give it a try (it is a lot less painful to use VMWare/Windows 7 on my Macbook now that I have a solid state drive).  I got a much sharper image from DSS.  I saved it as a 32-bit/channel rational FITS file out of DSS, then processed as usual in StarTools.  I’m having trouble getting as much color to show up as with the Nebulosity-stacked image, but looking at a bunch of M3 images on Astrobin I think the DSS-stacked version is closer to that average.  Here they are together so you can decide:

The Nebulosity-stacked image (above) is certainly more colorful, but the more selective DSS-stacked image has sharper, better-resolved stars.  I wish I could get Nebulosity’s colors with DSS’ sharpness.  I guess I could use DSS’ quality sorting to decide which subs to stack in Nebulosity, then have the best of both  worlds.  It’s a bit of a pain, but I could try that.  

Here it is:

It's the best of the lot, in my opinion.  I did encounter what appears to be a bug in Nebulosity 3.2: when I checked off subframes to skip and then tried to use the automatic alignment star selection, the selected star was lost when the routine came to the skipped subframes.  I guess I should report this.  

PicGoto Voltage Switching

16 Mar 2014.  I built and tested the PicGoto voltage reducer last night.  To recap the issue, PicGoto normally drives the motors at 12 V.  This allows faster slews than the 6 V the original motor driver circuit used, but because it’s using 12 V even when just tracking, the RA motor gets hot.  Reducing the input voltage solves the heat problem, at the expense of slower maximum slew speeds.  Ángel Caparrós on the PicGoto Group recommended another solution, a circuit that uses the output of the LED signal, which comes on only at higher motor speeds, to switch a second voltage regulator between 12 V when the signal is there and 6 V when it is not.  This cost about $5 in additional components.

So I built the thing on Veroboard.  Here’s the layout and a couple of pictures:

I wired this in parallel with the LED signal, and maybe that was a mistake.  I had hoped the LED would still come on normally, but it doesn’t.  Another problem was that I still had to reduce the maximum slew speed from 30x down to 25x (and this hasn’t been fully tested on the sky, so I’m not certain that 25x is working).  The voltage regulator on the new board gets warm, and a couple of times I lost the ability to slew (that might be from overheating, or it might just be the kludgy USB-serial-Windows 7-VMWare-Mac way I’m running it; this is prone to some problems too).   The good news is that the RA motor stays cool as a cucumber.  It would probably be worth trying unplugging the LED to see if that brings the voltage output back up.  I guess more questions to the PicGoto group are in order.  

The Meaning of "Cheap"

15 Mar 2014.  It occurs to me that I probably ought to justify the name of this blog by defining what I mean by “cheap” astrophotography.  This turns out to be more complicated than I originally imagined, because the cost strongly depends on what you want to do.  So I’m going to present several scenarios along with their costs, and end with what I’m actually using.  In each case I’ll list what I have or happen to have used; this doesn’t constitute an endorsement nor is it necessarily the best setup (in fact, almost always it won’t be the BEST, except possibly in the sense that it is good value for cost).  The listed prices are approximate, but close.  In all of this I’m going to ignore one of the most expensive components, the computer that is running the scope and mount and doing the image processing.  For the record, I use a MacBook Pro that was bought by my work (so for me it was free), but the model I have would be about $1500 new.  A $300 used laptop would probably be adequate for most things, but I’m going to ignore the computer in what follows.

The cheapest way to start in astrophotography is to do wide field or star trails shots.  For that, what you need is quite modest:

Starscapes	Model	Mfr	Condition	Price
Camera	PowerShot A560	Canon	new	$100
Tripod	"spider"	some off brand	new	$10
Stacking software	Deep Sky Stacker		new	$0
Total				$110

I’d consider the next step up in cost and difficulty to be lunar/planetary astrophotography.  Now you need a telescope and some means of pointing it and tracking the sky (although your tracking doesn’t have to be great for this kind of astrophotography, because you are taking short exposures).  I’ve included the CG-5 mount, which you can get used with motors for around $200.  My AT8IN scope is not really ideal for lunar/planetary work; you really want a longer focal length than the 800 mm it has.  That’s partly why I included the 3x Barlow as a necessary item.

Lunar/Planetary	Model	Mfr	Condition	Price
Mount	CG-5	Celestron	used	$200
Scope	AT8IN	Astrotech	used	$350
Imager	c270 HD	Logitech	new	$30
3x Barlow	3x	Meade	new	$40
Telrad sight	Telrad	Telrad	new	$40
Stacking software	version 6	Registax	new	$0
Total				$660

The next step, to deep sky imaging, adds cost and complexity.  You could do afocal astrophotography with a point-and-shoot camera (and that’s how I started), but I’m skipping that step here and describing the bare essentials of what I now use, a low-end CCD on an autoguided mount.  

Deep Sky	Model	Mfr	Condition	Price
Mount	CG-5	Celestron	used	$200
Scope	AT8IN	Astrotech	used	$350
Imager	DSI Iic	Meade	new	$250
Guide scope	9x50	Celestron?	used	$20
Focal reducer	0.5x	Antares	new	$25
Guide camera	DSI Ic	Meade	used	$80
PicGoto	Simplificado	Me	new	$40
Telrad sight	Telrad	Telrad	new	$40
Mapping	version 3	Cartes du Ciel	new	$0
Planetarium	ver. 0.12	Stellarium	new	$0
Stacking software	Deep Sky Stacker		new	$0
Post-processing software	GIMP		new	$0
Total				$1,005

Finally, here’s what I actually have and regularly use.  In addition to the AT8IN scope, I also have an Orion ST-80, which I originally bought to use as a guide scope.  Later I got a 9x50 finder with the AT8IN that was a lot lighter (and therefore more friendly to my mount, which can barely handle the weight I’m putting on it).  I started using the 9x50 as my guide scope and found the ST-80 could be used for wider field of view shots as long as I used a filter to cut out the UV and IR that cause pretty bad chromatic aberration with the ST-80’s non-apo doublet lens.  My current practice also uses a couple of pieces of software that are not free but are quite inexpensive.  I control my cameras with Nebulosity and also use that software for stacking.  I use StarTools for most of my post-processing.  I consider both these pieces of software to be well worth their modest cost.  Some of this is no doubt driven by the fact that I’m a Mac guy and both of these software packages have Mac-native versions that work great.  

Current Rig	Model	Mfr	Condition	Price
Mount	CG-5	Celestron	used	$200
Scope+rings	ST80	Orion	used	$80
Scope	AT8IN	Astrotech	used	$350
Imager	DSI Iic	Meade	new	$250
Guide scope	9x50	Celestron?	used	$20
Focal reducer	0.5x	Antares	new	$25
Guide camera	DSI Ic	Meade	used	$80
PicGoto	Simplificado	Me	new	$40
Telrad sight	Telrad	Telrad	new	$40
Imager	c270 HD	Logitech	new	$30
3x Barlow	3x	Meade	new	$40
UHC-S filter	1.25"	Baader	new	$70
Electronic focuser	AccuFocus	Orion	new	$75
Focus controller	FCUSB	Shoestring	new	$79
Imaging/stacking software	Nebulosity	Stark Labs	new	$80
Post-processing	StarTools	Silicon Fields	new	$60
Total				$1519

So I guess my $1519 bottom line isn’t exactly cheap, but it lets me do wide field, lunar/planetary, and reasonable galaxy/nebula astrophotography for a price that is about the same as most people’s camera or mount alone, so I still feel pretty cheap.  Fortunately, I didn’t get this all at once either.  These purchases have been spread out over about 3 years, so I didn’t feel them very much.  

My current deep sky imaging rig.