Thread: Sketching tips
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Old 11-10-2010, 12:40 PM
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mental4astro (Alexander)
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Join Date: Jun 2008
Location: sydney, australia
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Quote:
Originally Posted by Paddy View Post
Ok, I'm finally getting the nerve to try sketching globular clusters. I have no problem imagining sketching fainter ones with no resolvable stars. Just shading. But does anyone have some tips for sketching the very close and complex ones? How do you approach something like M22, or even 47 Tuc or Omega Centauri? Through a 16" scope, these are just overwhelming.

Any ideas will be greatly appreciated.

Said in his very best Irish accent:

"Good God, man! How many Guiness have you had this morning so far? Looks like one too many, and a Leprechaun has escaped into the belfry!"

The way I see it, in attempting something like a globular cluster, is the need for a good and constant scale, leaving the huge number of stars aside.

For this I have a couple of ideas:

1: locate three easily recognisable mini-patterns. Note these first as your reference points, and develop the drawing around them.

2: make yourself a reticle like I did (see pics & details below). This tool can assist with identifying the reference patterns and their scaled position. I used mine for the first time with the sketch I did of NGC 253 shown in the October Challenge.

But, one word of caution- unless you have a tracking mechanism on your scope, this reticle EP can drive you crazy trying to reposition the primary pattern back into position if you rely solely as your grid scale drawing method. Though I've only had one chance to use it so far, if your scope is only push-pull, I'd suggest this reticle idea only to find and position your reference "patterns". Attempting something like a GC will proove neigh impossible. Once you've got you reference pattern settled, change the reticle EP for your prefered visual EP, swapping to the reticle as needed to check on scale.

3: Start on a less populated GC to get your eye in.

4: Several nights viewing to complete the sketch patiently.

5: Use a medium to high power EP to limit the number of stars and reduce the confusion in relocating where you were. This doesnot need to be a complication once your scale has been set either.

I made the reticle EP using a cheap 2" eyepiece, here a GSO 2" SP 32mm ($49 from Andrews), and optic fibre fixed in place with epoxy glue and placed onto the field stop which is where the focus of the EP occurs. I might get a 2" barlow now to kick up the power for small objects, and do the same reticle pattern to a 25mm 1.25" EP as one scope I have only uses 1.25". I might also add another few fiber strands to make a finer set of grids.

The pictures show the reticle set on the field lens side, and a view through the EP.

It works so surprisingly well, and without any type of illumination.

A globular cluster, heh! Another challenge to tackle.
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