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Posts Made By: Alex McConahay

September 1, 2012 07:16 AM Forum: CCD Imaging and Processing/Deep Sky

M27 - C14 Edge F7.7 Narrow Band

Posted By Alex McConahay

Very nicely done, Mike. I hope to get that good someday.

Alex

September 7, 2012 09:25 PM Forum: Home Observatories

Dewed Telescope

Posted By Alex McConahay

I do not have much experience with dew, but keep an old hair dryer out in the observatory just in case.

I would avoid any capping of a wet scope.

Alex

September 12, 2012 10:13 AM Forum: Equipment Talk

Need some help ASAP

Posted By Alex McConahay

Orion and others make motors that can be retrofitted to a mount. That looks like a CG3 or so. Call them and ask them.
Alex

September 12, 2012 10:15 AM Forum: CCD Imaging and Processing/Deep Sky

M27 - NII, Ha, OIII

Posted By Alex McConahay

I never knew that extended nebulosity surrounded the main dumbbell until I found it in one of my narrowbands a couple of weeks ago.

Good Job, Mike.

Alex

September 17, 2012 07:40 AM Forum: Telescope Making

need advice on movement of mirror box

Posted By Alex McConahay

You cannot finish the mirror box until you have built the whole "tube" structure.... (unless you are a really good engineer to know just what the weights are and do a whole lot of good calculations.)

THe ease of movement depends on the friction and stuff in the bearings, but-----it depends a lot also on the balance of the assembly. If you do not have the whole tube built, you have nothing to balance the weight of the box.

What happens is that there is this number (moment arm????? correct me you engineer types) where the five pounds of secondary cage/focuser/secondary/etc. has to balance the 20 plus 29 some pounds of mirror box/mirror. It does this by being put on a lever some distance away. The fulcrum around which this assembly rotates is the center of your bearing.

To balance a 50 pound weight one foot from a fulcrum point, you need to put those five pounds ten feet away from the fulcrum point. (50 x 1=5 x 10) Of course, the weight you are trying to balance is not at the fulcrum point, so you must be even further away. Multiply the weight of the secondary assembly by the distance from the fulcrum to get that magic number. Then multiply the weight of the mirror box from the fulcrum point (bearing center). These two magic nbumbers must be equal. YOu get them equal by manipulating the position of the bearing, thus the distance from the centers of weight to the fulcrum point.....(By the way, it is not that simple because the trusses themselves have weight--which weight is distributed along their length!!!)

THerefore, you need the tube assembled before you locate the bearings.

What you have to do is not put the bearings on.......
Assemble the whole tube, mirrors, trusses, finder scope and all, and test that the thing reaches focus as it should.

Then put the assembly on it side on a wooden dowel or pipe so that it will balance properly. (Find its center of mass.)

That center of mass is where the center of your bearing should be. ONce you know it, put the bearings on the mirror box.

By the way--it sounds like you may need to add something to the top of the secondary cage to change the balance point.

Alex

September 13, 2013 07:52 AM Forum: Home Observatories

Yard/Garden shed observatory

Posted By Alex McConahay

Check out what I did for mine.....

http://alexastro.com/Alex%20Home%20Page/Equipment/outhouse/outhouseindex.html

It might give you ideas.

Alex

October 23, 2013 04:24 PM Forum: Refractors

Daytime Photography with Refractor

Posted By Alex McConahay

By definition, a Petzval allows flat field photography. Of course, it depends on the quality of the implementation. A field flattener for the TV 85 would also work. If you already have the 85, that is a much less expensive route. You will not find a much better scope than the 85 (or other tele-vues), and you already have it.

Be aware that you will probably also want an extender because I doubt the TV 85 would come to focus without it (not enough out travel once you remove the diagonal). These are relatively simple, non-optical, so they are not that big a deal.

Alex

January 14, 2014 06:39 PM Forum: Equipment Talk

battery packs

Posted By Alex McConahay

Those battery packs you see from Celestron and others (and from your local Walmart and Kmart Auto section) are, deep down inside, a $15-30 battery, readily available on the internet, with some interesting connectors and lots of casing.

If what you want is cost and weight effective power, I would suggest you google "SLA 12 volt battery" You will find any one of a thousand suppliers. These are what are used inside the power packs you are asking about.

While you are there, buy yourself a separate batery charger designed for these things ($8-15). I should say, though, that you may already have one or more of them around the house.

THen go down to your local Radio Shack, auto parts store, electronics warehouse, whatever, and buy yourself a cord, or whatever connectors you want, and make up your outlet arrangement.

You will have the functional equivalent of the power pack for half the price, less weight, and smaller form.

(Now, whether they will be sufficient for your uses, that will depend on how much elecctricity you use. I simply do not have experience with dew, so cannot advise you there. )

Alex

July 31, 2010 09:38 PM Forum: Polls

Worst recent USA President

Posted By Alex McConahay

No death so horrible as that of a sweet, innocent theory by a gang of ruthless, murderous facts.

You are merciless.

Alex