DIY Dob Setting Circles

[mike-h]

After getting frustrated trying to locate objects with my Skywatcher 250px Dob I decided to look into buying some setting circles. However they looked like a pain to fit and use so I made my own. Here are some pictures:

I used a cereal box and sellotape. It took 90 minutes to make. One word of advice-make a prototype first to work out the correct length to ensure it wraps around the whole circumference.

I cut 8 thin strips of card from the box using a stanley knife (14mm by 204mm).

I marked the angles in 5 degree increments. I then used 25mm sellotape to laminate the front of the card (folding it over the edges). I then sellotaped the 8 sections together. I then stuck 13mm double sided tape onto the back to laminate the back and to stick it around the dob base.

Then I made the pointer out of card - it represents a 10degree secton. I then taped a pin to the middle. It attaches to the base with blutack.

The great thing is that there is no polar alignment.

1) I simply point the scope at any object (eg Saturn)

2) Then I find the az coords off stellarium (e.g. 251.3 degrees).

3) I then blutack the pointer to the lower base disc at that angle.

4) I can then get alt-az coords from stellarium for another object (eg M13 say). I then rotate the base until the pin points to the correct az coord. Finally I use the Wixey to raise it to the correct alt coord. It really works. Objects land in (or very near to) the FOV of my 32mm eyepiece.

I'm really pleased with it.

Mike-h

[Doc]

A very simple design that looks good and works a treat.

It's amazing how well these setting circles work.

Well done Mike.

[GazOC]

I made a set for a 8" Dob I had a few years ago, the feeling of excitement when that first object comes into the FOV is amazing!!!

[kniclander]

very neat very nice:) but why not just line it up on Polaris?

[mike-h]

I have a South facing garden and I can't see Polaris. Plus its not the brightest or most obvious star.

Mike H

[philsail1]

That's a very neat idea Mike - and so simple to make too!

(Why don't these major scope manufacturers do something like this - instead of the complicated set ups they sell).

Very well done indeed.

philsail1

[mike-h]

Thanks Phil. I hope some of the beginners find it useful. I know that I would have done this months ago. Thanks to people on SGL who got me thinking of the idea!

Mike-h

[albedo0.39]

I like the idea a lot and it does you credit for working out an original concept. I had planned, printing my setting circles from a website and then cutting it out and sticking it to the base, but I like your idea better because you move the indicator to the actual position.

Neat...

[mike-h]

Exactly! That's the best thing about it. Alignment is dead quick and easy if you move the marker instead of the scale.

Mike-h

[rwillett]

At the risk of jumping into a thread, I wrote a (free) website for generating setting circles of just about any size. Have a look at http://settingcircles.robertwillett.com.

You can draw both flat circles and strips to wrap around a base (as above).

All the best,

Rob.

[kniclander]

Rob, for the linear strips is there a way the maximum radius an be increased as I would guess the radius of my dob base is around 12 inches?

looks good though and thanks for posting it:)

[rwillett]

The problem is not the PDF generation, it's how you print it. A 12" radius produces a linear strip 75" long. Thats over 6ft (or around 2m). You would need a plotter to print it out and most people don't have plotters. Thats why the largest sheet you can print on is A0, and even at that standard size, 33" x 46" many print shops would balk at. The largest size that would fit on a A0 page is around a 200-220mm radius (8" - 9" radius, 16"-18" diameter).

I could look at custom page sizes but how would you print it?

Rob

[kniclander]

oh I see - I had assumed that it would print out lots of little strips that you would stick to the base one by one. I don't have access to printing any paper larger than a4 anyway. No prob.

cheers

dan

[Doc]

I used Robs program to print my dob circle and Rob it's a great little program Thanks.

Put it onto a memory stick and take it to Staples they print A0 for if my memory serves me £2.47 a sheet.

[Macavity]

I have solved the (general) problem before, by using some... Graphics package. You could draw several strips etc. side by side. Naturally, you do have to "join" them later. Fiddly, and wasteful in the (sizing) experimentation? But the eventual accurate and professional look has many attractions!

Now, if only they made a "Wixey" with backlighting.

My experiments re. THAT were far less successful.

[mike-h]

Like I said above, I really wish I'd done this as soon as I bought my Dob. It would've saved so much wasted time and frustration (at one point I thought about selling the big dob in order to buy a small GOTO).

So these setting circles would be very useful for a beginner with a dob. It never occured to me when I bought the dob in February to make setting circles-indeed it was reading posts on SGL that led me to do it.

I am wondering whether to re-post this in the beginner's section.

The reason for this is because (as a beginner) I had assumed the DIY astronomy section was about making your own scopes so (despite using SGL for 5 months) I never bowsed this section until 2 weeks ago.

I don't know if it's the done thing on SGL to post the same thing in two places. It would just be nice if this post was easy for a beginner to 'stumble across'.

Any thoughts?

Thanks

Mike-h

[ringz]

Mike-h,

You could always post a link to this thread in the beginners section. No-one will object to that.

--

Martyn.

[mike-h]

Great idea Martyn.

How do I post a link?

Thanks in anticipation

Mike h

[ringz]

Mike,

Well to the right and at the top of this topic list is an object (#1 (permalink)). Right click on permalink , select copy link location (at least that's what it's called in firefox) and the appropriate URL that points to this topic will get stored in the clipboard.

Now you can start your own topic in the beginners section and paste the link there.

I hope this helps and isn't total gobbledygook

--

Martyn

[mike-h]

Cheers Martyn

I'll give it a go

Mike-h

[Dante]

Hello Mike-h. I read your thread with interest. Like yourself I have never browsed this part of the forum for the same reasons.

I have been thinking about using the setting circles concept (DIY of course) on the GOTO mount for my Skywatcher OTA using a similar approach. Do you think it would work? The circle is very much smaller than your DOB. The scope moves under power all the time so I can't manually move it (at least I don't think so) but I would be able to use the fastest slewing rate if needed.

Perhaps I am barking up the wrong tree:icon_confused:

Danny

[Dante]

Forgot to ask. You don't polar align. Is that because you use Stellarium co-ords for ensuring thatthe circle is correctly sited?

Danny

[Macavity]

Do you think it would work? The circle is very much smaller than your DOB. The scope moves under power all the time so I can't manually move it (at least I don't think so) but I would be able to use the fastest slewing rate if needed

Things like THIS work rather well. But admittedly with a manual mount - the Giro III. I've also used the general idea with an EQ3-2 rotated to make a quite effective manual (geared!) Alt-Az mount. With a basic (intuitive) "One star alignment", quite good enough to get the object within a 2-4 Degree Scope/Finder field. Or, at worst, you have to set the Altitude accurately (with the Wixey) and "scan" a bit in azimuth.

[Dante]

Things like THIS work rather well. But admittedly with a manual mount - the Giro III. I've also used the general idea with an EQ3-2 rotated to make a quite effective manual (geared!) Alt-Az mount. With a basic (intuitive) "One star alignment", quite good enough to get the object within a 2-4 Degree Scope/Finder field. Or, at worst, you have to set the Altitude accurately (with the Wixey) and "scan" a bit in azimuth.

Hi

Had a look at the photo, not quite what I expected, however I am still toying with the idea and will probably get Autocad up and running and pull off something to trial. I may be off base here but I visualize something that is much simpler. Ideas are fine it's the application that matter - YES!

Danny

[mike-h]

Danny

Sorry I typed 2 replies and they would not post.

Mike h