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Posts Made By: Dave Erickson

January 6, 2014 09:17 PM Forum: CCD Imaging and Processing/Deep Sky

First of my December Images IC443The Jellyfish

Posted By Dave Erickson

Wow Floyd that is really nice! Dave

January 15, 2014 01:47 AM Forum: Equipment Talk

battery packs

Posted By Dave Erickson

Hi Brian,
All good advice. Prior to the remote setup I'd go to the field for several days and power was always an issue. I drained the car battery in the field more than once and needed to do something different. Here is an image of a DIY 3-bank setup with charger power-supply and both "visual" voltage monitoring and "computer" voltage and current monitoring. It is very heavy 75pounds, used AGM deep cycle sealed batteries, but worked. Three banks with 21 amp hours each. One bank for cameras, one for computers, and the third for mount and focus.

Best,
Dave

January 15, 2014 02:17 AM Forum: CCD Imaging and Processing/Deep Sky

Pacman nebula

Posted By Dave Erickson

Wow, beautiful...

January 16, 2014 04:06 PM Forum: CCD Imaging and Processing/Deep Sky

M51 Luminance data

Posted By Dave Erickson

Hi Russ,
That is a very nice image!
Regards,
Dave

February 8, 2014 11:21 AM Forum: Home Observatories

New Observatory Site

Posted By Dave Erickson

Hi Russ,
Looks like a very good site with a very good horizon. If I am correct on the approximate location sky is a Bortle 4 with very good southern and eastern skies. How is the southern and eastern horizon? Have you observed from there long? Nice to have utilities near by and good internet as well. Please keep us posted on your progress.
Dave

March 23, 2014 06:20 PM Forum: Telescope Making

Mystery Quartz Flat or Blank

Posted By Dave Erickson

quick way is to measure its density fused quartz and fused silica have a density of 2.2 gm/cc or (137.4)(lb/ft3). Measure the diameter and thickness calculate the radius pi*r^2*thickness is the volume measure its mass divide the mass by the volume and you get density. Looks polished on both sides you can also measure the refractive index by measuring the thickness then measuring the optical path using a traveling microscope. Optical path length =refractive index*Thickness... Fused silica should have an index of about 1.46 at 500nm... I have used both methods many times to sort out mixed materials...

March 26, 2014 08:50 PM Forum: CCD Imaging and Processing/Deep Sky

NGC1763

Posted By Dave Erickson

Roland,
Some great astro imaging, thats a beautiful optical system...
Dave

March 29, 2014 08:12 PM Forum: CCD Imaging and Processing/Deep Sky

NGC 1999

Posted By Dave Erickson

Hi Enrico,
That is very nicely done! And in addition to Roland's a perfect start to the 2014 season...
Best,
Dave

March 29, 2014 08:35 PM Forum: Telescope Making

open OTA for refractors???

Posted By Dave Erickson

Hi John,
With all your experience, I think you know the answer very well...Aside form being minimalist is there some compelling reason for an open tube, so many disadvantages strength and associated flexure, even a truss structure with long throw and small base has flexure issues, air currents dirt and dust.. 180 is not that big I'd go with a carbon tube if you are concerned with weight, an aluminum tube will be a lot simpler and less expensive. These are all things you know well from your years building and rebuilding... No irreverence intended just an affirmation of what you already know...
OH and building a refractor of that size and speed is one #$%% of an accomplishment, hats off to you...
Best regards,
Dave

April 15, 2014 12:47 AM Forum: After Dark

The Rusty Moon

Posted By Dave Erickson

Hi Andy,
Yes both from Huntington Beach Ca and the remote observatory in the southern Sierra Nevadas Regards,
Dave