Image of the day

Captured by
Craig Bobchin

Coathanger CR 399

About Astromart

My Account

New to Astromart?

Register an account...

Need Help?

Posts Made By: dan hilts

October 27, 2007 08:58 PM Forum: Eyepieces

new Hyperion 24mm?

Posted By dan hilts
<>

Not at all the same. The 24mm will give more magnification so you will see a smaller portion of the sky in one view, about 20% less.

In the 1.25" size, the widest field you can see is from a 32mm 50 degree eyepiece which will be about the same as the 24mm Hyperion at 68 degrees. The portion of the sky observed is the same, the 24mm just gives a more magnified view. Unfortunately, if you want low power wide field views, you need 2" eyepieces.

hope this helps,
dan

October 31, 2007 04:18 PM Forum: Equipment Talk

CCD Building question

Posted By dan hilts
Hi Dave,

I don't want to burst your dreams but...

I have over thirty years experience in the electronics industry and I don't think I would tackle a project like this one. Twenty years ago I might have but not today. Components,(if available) will not be cheap and building from scratch is a difficult task. Keep in mind, components will be small (actually tiny)and will require proper handling techniques to prevent damage. The final circuit will be complex as far as project electronics go and may require some trouble-shooting to get it up and running. You will need some test gear.

You may be able to find a kit available somewhere or perhaps only a bare circuit board you can stuff with components. Unless you have a good amount of experience behind you and have access to a lot of resources, this is not going to be a money saving project. My advice would be to settle for a less expensive imaging method such as web cams or one of the more modest imaging systems from Meade or Orion. These are well suported and won't break the bank.

good luck,
dan

November 1, 2007 02:08 PM Forum: Refractors

Spot diagrams / How do you read them? Pt. #1

Posted By dan hilts
Spot diagrams show how an optic focus various colors of light. It is based only on the theroectical performance of the design, not on errors in workmanship or flaws in the glass. The diagrams you have been given appear to be for a refractor. Blue light is on the left, infrared is on the right. The image has been focused for green light (centre column).

The top horizontal row is the "on axis" plot. It shows how the various wavelengths of light are focused in the centre of the optical path, "on axis". Note that when green is focused, there is an expanding amount of defocus across the spectrum, ( secondary color)

The middle horizontal row is for points that are 0.25 degrees off axis and the bottom row is for points that are 0.5 degrees off axis. Note that the green light off axis is starting to stretch out. The optic is no longer creating nice sharp pin points. This is due to the optics design leaving uncorrected astigmatism and/or coma.

Inside each spot is a small circle representing the Airy disk. A scope cannot create a spot smaller than the Airy disk and if all points are inside the circle then that is as good as it can be.

hope this helps,

dan

November 1, 2007 02:18 PM Forum: Refractors

Spot diagrams / How do you read them? Pt. #2

Posted By dan hilts
The plots in #2 show much less defocus of the colors across the spectrum. There is very little outside the Airy disk until you get into the ultraviolet and infraed regions. There would be very little color (very close to none) for visual use.

Also note that there is less distortion in the off-axis points in #2 compared to #1. The second optic would have bettter off axis images.

I would say #1 is an achromat, #2 is an Apo.

again, I hope this helps,
dan

November 7, 2007 10:27 PM Forum: Beginning Astronomy?

Mounted (Green) Laser Pointers and the Cold

Posted By dan hilts
Why not use an external battery to power the laser? You could assemble a quick and dirty regulator to work off a 6 or 12 volt battery and one of these should run the laser for next to eternity. Or add an external battery pack and use D cells. These will outlast AAAs.

dan

November 9, 2007 09:54 PM Forum: Refractors

Why is lead "faster"?

Posted By dan hilts
<>

Lead oxide has been used in glass production for a very long time, particularly in crystal. It helps to make a glass very transparent.

I don't know anything about Vixen's production but the glass industry in general has been moving away from glasses produced with lead. The lead in the glass is not a problem as it is bound pretty tightly but there are environmental concerns with the manufacturing processes and the waste products. Many of the old "standard' glasses have been replaced with lead free types. Perhaps the optical quality was not available for Vixen design with new glasses.

hope this helps,

dan

November 11, 2007 06:06 PM Forum: Eyepieces

barlowing the new Hyperion 24mm?

Posted By dan hilts
Harry,

I saw your post last night and I was headed out for first light with my new 24mm Hyperion. I was using my homebuilt 120mm F12.5 refractor.

First off, if the 24mm has 20mm eyerelief, it certainly didn't feel like it. More like 15mm.

Barlowing didn't really change the eye relief. I don't have a TV barlow but I did try it in three others. Seeing was not the best but the sky was fairly clear. I tried a couple of targets that were well off the horizon.

I used an Antares 2"-1.6X barlow, a GSO 2"-2X, and an Antares 1.25"-2X. The 24mm Hyperion looks really funny (awkward) on top of a 1.25" barlow. Other than that, I didn't notice a problem. I did manage to split Iota Cass as a nice tiple and Zeta Aquarius, a tight double. I cheked out the Auriga clusters as well as M35, and M42 and others. Mars was just too low to get a good view.

Overall, I think the 24mm took to a barlow as well as any eyepiece would. I like barlows and don't have an issue with using one.

clear skies,
dan

December 10, 2007 08:43 PM Forum: Telescope Making

Can you help ID glass for an objective

Posted By dan hilts
Anthony,

This is only a suggestion.

You may be able to get some data on the flint blank by determining the glass density. The flint glasses have enough difference in the densities that it is sometimes possible to isolate the glass. This won't give exact indices or dispertion values but it will narrow down the choices. I would doubt the F621 refers to F6 from Hoya. (At one time I tried hunting down F628 and I came up empty. I would love to hear if anyone else has something to offer)

The crown glasses are often very close to each other in densitiy so this technique won't help much with your problem there. However, it may be reasonable to go with what you have and take the glass to be as labelled, BSC2.

I have an old B&L glass catalog that shows a Borosilicate Crown 1.517, 64.5 and a dense flint 1.621, 36.2. I can send you a copy if you PM to me.

Alternatively, grind and polish the glasses into lenses and measure everthing you need to know. Then regrind into the lens you want.

good luck with your project,
dan

December 14, 2007 03:48 AM Forum: Beginning Astronomy?

refractor disassembly

Posted By dan hilts
Jack,
It would seem that getting the loose nut out is going to be the eay part. Putting it back in place to fix the old plate or install a new one plate, is going to be tricky part. I have had some success in reaching into tight spaces by taping a nut to the end of a stick pupose made for the task at hand. You could cut a long reach stick out of a sheet of plywood that may put the nut back where you need it. Once the nut is gripped by the screw, the assembly can be tightened until the masking tape looses its grip. You may have to live with a piece of tape inside the tube but it should be out of view.

good luck,
dan

December 15, 2007 02:57 AM Forum: Beginning Astronomy?

How Bad is this $50 Meade Diagonal?

Posted By dan hilts
Paul,

I have one of those diagonals. It is not entirely plastic, the mirror is glass.

I use mine on a light weight 80mm finder for low power use only. For that it is OK.

Optically it may even been OK as very little of the mirror surface contibutes to any one point in the final image. However, you can do much better and will probably notice a difference at anything other than your lowest power. I would not want to hang too much weight on this plastic body. There are lots of well made lower cost dielectric diagonals on the market now that weren't available two years ago.

Treat yourself to an upgrade. It's Christmas time.

clear skies,
dan

Funding Member

Sponsors


View all sponsors

Search