Astroboffin

4 hours ago, The Admiral said:

Forgive me asking a stupid question, but how is binning done on 4-pixel arrays?

Ian

you can't hardware bin a colour camera, whether it be OSC CCD or DSLR, but I guess you can software bin, but have no clue how as never needed to do it.

AB

 

Hi,

first of all I am confused by a few of your statements.

Using a focal reducer does increase your field of view, and the photons are spread over fewer pixels, but you will be getting more arc seconds of sky per pixel, so your pixel scale will go up.

so yes as you will be getting more light then you can lower the exposure.

as for binning, if,you bin 2x2 in the camera, and you have say 5 micron size square pixels, then after binning those pixels are now 10 micron size in effect and twice as sensitive as before so it makes the camera a lot more sensitive, but at the cost of halving the resolution, but you are still imaging the same amount of sky, so the image will be the same but lower resolution when binning.

binning in the software will not give you the same effect, as hardware binning in the camera.

so the reducer and binning are two completely different things, and binning in the software will not increase your FOV like the reducer will, so there is no way binning can take the place of a focal reducer, as it would have to alter the FOV of the image to do that, and it doesn't, it just lowers the resolution, but makes the camera more sensitive.

so the two things are completely different.

i hope that all makes sense, and is of some help.

AB

Saw this last night, superb way of protecting the little gold wires you are all talking about, using epoxy resin to encase the wires, which allows you to be a bit more heavy handed without fear of damaging them, would give a nice solid edge to scrape up too.

Of course you may already know about this idea, but I thought it was quite clever....

http://www.jtwastronomy.com/tutorials/debayer.html

AB

You could do what I sugested in my first post, and remove the field flattener lens from a Meade or celestron reducer, it is very very simple to do, when you unscrew the locking ring, stand up on a piece of cloth and the lens comes out in two pieces with a small plastic spacer between, lift the top lens off ( this is the flattener, it is nearest the camera end) and then the little spacer, then put the casing back over the reducer lens and put the locking ring back in.....simples, now you just have an f6.3 reducer.

I have removed a few of them to fit into a 2" cell so they would fit inside my 2" focuser, rather than have to screw on the back with the SCT threads, but I kept the flattener in also.

Can't see why it would not work, and a much cheaper option.

AB

Ignore my earlier comment - I hadn't spotted that you were talking about the ACF

Yes me too, sorry

Should read the post properly before answering...

Regards

AB

Hi all,

I've been looking into focal reducers for my LX200 10inch (ACF). Every f/6.3 reducer I find seems to also correct the image aswell. All I'm looking for is a focal reducer that only widens the fov and provides a faster aperture. Any ideas?

Thanks

What would you not want to correct the field too, once the reducer has done its job you will get a large amount of field curvature issues and you will need them corrected by the flattener.

If you really don't want to correct the errors, then if you get a Meade or celestron f6.3 you have two sets of lens in them, and you can remove the one nearest to the camera and that is the flattener, and just leave the reducer in place......simples..

Regards

AB

The sketch does half-steps too as it alternatively energises both coils in between the single coils. If you look at the sketch there is an array of values you should be able to see how it works. Plus I have it geared down further by the belt & pulleys I use. The main thing is this is not a completed design and I like the idea of people experimenting with it and and adapting it for their own needs. Post some pics when you have it working

I will do, as I have all the bits arriving over the next week, so the fun will start, although by the sounds of it, I have done what can be a awkward bit and got all the software installed and up and running, but using my Arduino Uno ATM.

I am going for a design that see just the motor on the focuser and the rest of the electrics and control boards will be in a project box on my mount about a metre away, so I will need to extend the 5 core motor cable, and am thinking of using a Cat5 cable with sockets

On the box either end to connect all together.

AB

Ok, so I have figured out this stepper motor issue with the steps, the motor I am getting is the 12v, 64 step with a 1/64 gear inside, version of the one the OP used, which means that it gives 64x64 = 4096 steps, but as in the sketch the motor moves 8 steps per driver step, that means 4096\8 = 512 steps per Rev, so I will leave set at 8.

But I can see the motor the OP used was a 32 step with 1/16 reduction gear, which gives 32x16= 512 steps, but for that motor to get the full 512 steps the MOTOR_STEPS_PER_DRIVER _STEP would need to be set at 1

Well it makes sense to me now anyway, but worth knowing if you are looking at buying one of these motors, as they all look the same on eBay, but they are not.

:)

AB

That's how I understand it (now)

Makes interesting reading, thanks for posting the link.

Yes very interesting, but I stand by what I said before, I still think you have it the wrong way round, if you take a wide field image with the small 66mm f4.8 scope you can get away with it a tad out of focus without it damaging the image too badly.

But in contrast if you use an 2000mm f10 scope and image Jupiter for instance, focus is absolutely critical for a half decent image.

And I think on the site that was linked it says that but in a very very scientific way, which is very hard to decipher.

The in focus area of the f4.8 scope is much smaller due to the large field of view, whereas the f10 scope has a much bigger in focus area because of the much smaller FOV, so consequently much more critical as much more noticeable......

So let's here from others......on this

AB

The MOTOR_STEPS_PER_DRIVER_STEP value is how many 1/2 steps the motor takes for each step (Position property) from the Ascom driver. I originally had the motor cycle through all combinations of the motor pins to simplify the programming which gave multiple motor steps per driver step. I realised this could be made finer by just making it step once per driver step so I changed the sketch to accommodate that. The MOTOR_STEPS_PER_DRIVER_STEP value is set to 8 by default to mimic the original behaviour but it can be changed to whatever suits you. Remember - the motor always does 1/2 - steps but they are always the same size.

I think some of the steppers on ebay like the one I used have internal gearing from 64 to 512 steps per revolution - check the datasheets carefully. Hope that helps.

This is the spec sheet for the motor I have found, and the others I have seen 12v and 5v are the same apart form voltage, 64 step, 5.625 degrees per step, so 64 x 5.625 = 360 degrees.

Can't find any with 515 steps,

So with your method of being able to reduce that figure from 8 to 1 does that then give me 512 steps, per shaft Rev, assuming there is no internal gearing

Nice explanation... I can sit down now 

If I'm reading the info on this  http://www.astropix.com/HTML/I_ASTROP/FOCUS/DEFS.HTM  page correctly, I think the depth of focus changes as the square of the F number.  So an f10 scope is more forgiving than an f4.8.

Noel

I think that is the other way round, f4.8 is more forgiving than f10, as f10 is far More magnified, than f4.8, the field of view is much smaller.

Well that's my understanding anyway

AB

I have no experience of the Skywatcher motor but as you, I also suspect that it woud provide finer if not as precise control as the stepper.

The 12v motor will provide more torque and this "mod" seemed like the logical choice given that pretty much everything else astro wise is 12v, except the 5v stuff

As far as I know focal length has nothing to do with focus, it will be the same what ever the scope...I stand waiting to be corrected on this.

You may well be right on the MOTOR_STEPS_PER_DRIVER_STEP value, I have not tried altering this value.

If it does do what you hope, from what I can gather on the web the motor has about 512 steps per shaft revolution. So if you change it to 4 from 8 it will be 128 steps(512/4=128)

As with most things try it and see what happens, some of the best discoveries have been found that way.

Yes agree with most of that, but not sure about the bit to do,with the steps on the mentioned stepper motor, it is reported to be a 64 step motor, not 512, as it says that in the write up on these motors each step is about 5.3 degrees, so 64x5.3= 360 approx one full revolution.

By lowering that number from 8 to 4 I thought they became, 1/4 steps so in effect the actual steps get smaller but more of them, so 64x4 =256 steps per revolution, as each step moves about 1.3 degrees........

That was my understanding but maybe the OP can step in and explain.....as we seem to have completely opposite answers to this one....lol

Thanks anyway

AB

I've gone for a direct connection, using the 10:1 shaft on my focuser and that works a treat! I think direct to the normal rate shaft would not be fine enough IMHO. 

Hope that helps.

That is my worry

I have a standard skywatcher DC motor fitted ATM on the rough focus shaft, (direct drive) of my William Optics ZS66, and can get very good fine focus with that using the Hitecastro DC focuser controller using the DC motor step routine built into it.

So how much better would this 64 step, stepper motor be, apart from the obvious of incremental steps and being able to move back to exact position.

The other thing is that I am going to go for the 12v version of the stepper mother used here by the OP.

Am I right in assuming that on a 66mm f4.8 scope focus is not quite as critical for wide field deep sky imaging, as it will be for planetary imaging on my f10 8" SCT, this is the one I want the stepper motor for, as I am getting a new Crayford focuser on the back.

Regards

AB

I have installed all the software from sourceforge, and all worked perfectly first time, with no issues at all, trying my windows 8.1 laptop next.

Still sorting out which steppers to buy, I think as all my kit is run from a purpose built 12 power hub, I may go for the 12v version of the motor used at the start of this thread.

I realise it is only a 64 step motor as I mentioned earlier, but I notice now that you can alter the sketch from 8 steps per instruction to anything down to 1 so does that mean that it in theory becomes a 256 step motor if I reduce to 4 as shown here in my screenshot.

It will be fitted straight onto my focus shaft I will not be using the 10:1 knob, failing this, would a better motor with more steps be needed, and if so which one, as I don't want to alter any of the provided code, well I couldn't if I wanted too......lol

So I just want to connect a motor and it works straight away, so is the sketch and code purely written for the motor used at the start of this thread or will it work with any available stepper motor

Don't forget the advantage in the pulley system. Mine is 4:1, so 1 revolution of the coarse focus knob = 256 steps. You could easily make it 5:1, 320 steps.

When I made mine I had doubts on whether the motor's steps were fine enough but it was so cheap I figured it would be worth a go and maybe upgrade later. As it turns out it is more than adequate, I doubt that the movement would be quantifiable if it was much finer.

Hi all,

Fantastic thread, just wanted to quote on this

I understand that with the Gears and pulleys you will get very fine focus, but if, as I want to, you have a direct to shaft connection, then one Rev of the motor is one Rev of the focus shaft, so with the motor mentioned and used throughout this thread that's only 64 steps, as opposed to 256 with a 4:1 pulley system.

So is 64 steps enough, or is there a different motor I could use, as I have to have a direct connection ?

Regards

AB

I agree.

I can confirm that it is a 750k

http://www.p4c.philips.com/cgi-bin/dcbint/cpindex.pl?ctn=PCVC750K&scy=us&slg=en&mid=Link_Software

The 740k is called ToUcam Pro and the 750k is called ToUcam Scan as it was sold with a mounting harm to scan documents, quite weird actually

Yes I have found it, it is essentially the SPC880 but in a different housing for a different purpose, but exactly the same camera.

AB

The slightly older Philips SPC880nc shows up,as a 750k when you connect it to sharpcap, and those are the drivers you need so you can flash it, I have just flashed one for a member on here, for the cost of the postage, I have done over 50 of them for people, I can do the Toucam pro the toucam pro II the SPC880 and change them all to the SPC900nc, so if you are struggling let me know.

Regards

AB

Hi Guys thanks for all your suggestions but being a newbie to astro photography I think I may have discovered the problem. My webcam is actually an SPC880NC from Morgan not a genuine SPC900NC albeit I understand it has the same internals. I now need to find a friend with windows XP to flash it. Sorry for leading you all astray now the search for a friend with XP or buy a cheap XP PC

Thanks again

I have sent you a PM about the flash mod

AB

You only need the win 7 driver and it will work on 8 also

Here:

http://www.p4c.philips.com/cgi-bin/cpindex.pl?ctn=SPC900NC/00&hlt=Link_Software&mid=Link_Software&scy=GB&slg=ENG

Hope that helps

AB

I agree.

I can confirm that it is a 750k

http://www.p4c.philips.com/cgi-bin/dcbint/cpindex.pl?ctn=PCVC750K&scy=us&slg=en&mid=Link_Software

The 740k is called ToUcam Pro and the 750k is called ToUcam Scan as it was sold with a mounting harm to scan documents, quite weird actually

Ok good to know

Never heard of that one, sorry for doubting

:)

AB

Hi,

Are you sure it was 750k toucam and not 740k, I have never heard of a 750k

Not being picky, but for your tutorial purposes is need to be right.

Regards

AB