Butterfly cluster

[TrevorW]

Target The Butterfly Cluster Messier 6 or M6, and as NGC 6405

Scope: GSO 8”(200mm) F9 CF RC
Mount : Losmandy G11-G2
Camera: QHY 8 OSC CCD
Exposures: 15 frames 9 minutes per frame 2hr 15m
Date: 19/5/2012
Time: 9:00 – 12:00pm
Seeing : Very Good
Conditions: Cool night no moon usual suburban LP
Guiding: Orion SSAG on 72mm WO Mergz using PHD
Stacking: DSS
Processing: PS CS 3, Max DL
The Butterfly Cluster is an open cluster of stars in the constellation of Scorpius. Its name derives from the vague resemblance of its shape to a butterfly.
The first astronomer to record the Butterfly Cluster's existence was Giovanni Battista Hodierna in 1654. However, Robert Burnham Jr has proposed that the 1st century astronomer Ptolemy may have seen it with the naked eye while observing its neighbour the Ptolemy Cluster (M7). Charles Messier catalogued the cluster as M6 in 1764. It was not till the 20th century that star counts, distance, and other properties were measured.
Characteristics

Most of the bright stars in this cluster are hot, blue B type stars but the brightest member is a K type orange giant star, BM Scorpii, which contrasts sharply with its blue neighbours in photographs. BM Scorpii, is classed as a semiregular variable star, its brightness varying from magnitude +5.5 to magnitude +7.0.
Estimates of the Butterfly Cluster's distance have varied over the years, with a mean value of around 1,600 light years, giving it a spatial dimension of some 12 light years. Modern measurements show its total visual brightness to be magnitude 4.2.
Right Ascension
17 : 40.1 (h:m)

Declination
-32 : 13 (deg:m)

Distance
1.6 (kly)

Visual Brightness
4.2 (mag)

Apparent Dimension
25.0 (arc min)

[Ross G]

A nice photo Trevor.

I like the composition and the stars.


Ross.

[TrevorW]

Thanks Ross

[jjjnettie]

I like the star colours :) Thanks for the view.

[TrevorW]

Thanks JJ

[strongmanmike]

Quite nice stars Trevor...I am a little puzzled though, this cluster sits in a rather rich star field..?

Mike

[TrevorW]

Thanks Mike, I am too I would have thought with 9 minute subs and 2hrs data I'd get a lot more in the background (this has been an issue of late)


It's either a problem with stacking in DSS or my camera's not working as well as expected since I had an incident late last year with a bright band appearing across the top of subs

Any ideas would be appreciated, has it anything to do with the FL I'm capturing at, I did'nt use the reducer with this

[bmitchell82]

Trevor, grab a raw sub and put it in DSS in the top right hand corner is a black grey and white levels adjustment. grab the grey pointer and move it to the left. if you see stars there then you are killing them in your processing.

If they aren't there then your not capturing them in which case your bias and gain settings are wrong. The other point is that you may not be focused correctly or your collimation of the telescope is not right.

High F ratio hyperbols and compound telescopes require so little to be out of alignment and then your focus is shot.

Also be careful with minimum filters they kill stars faster than an explosive charge kills fish in a small fish pond. Better control of curves, high pass filters and highlights and shadows will produce stars that are not blown out and in general far better results. I personally do not like the minimum filter in PS because it isn't well suited to astrophotography processing for a mechanical error/defect.

Brendan

[strongmanmike]

Not sure...are you stretching the raw data :shrug:

Straight out of the camera there may just be the bright stars but some ddp and log stretching should reveal plenty

As a guide, HERE (http://www.pbase.com/strongmanmike2002/image/126692382/original) is what I got with about the same exposure length with the 6" Starfire

[TrevorW]

Thanks Mike and Brendan will try

Collimation may be an issue as I was just discussing this the other day with Marki, as sometimes it takes two heads to get these RC's just right

(Brendan, I don't use the min filter for just the reason you mention)