September Competition Theme - Star Clusters (2006)

Okay, Dave, I will supply the AP160 (and Greek weather) and you supply the AP1200GTO. :lol:

Done!

Seanie - whatever Anthony submits for this months competition is a joint submission

Woo hoo - how can we lose eh Anthony? :lol:

Dave,

Indeed how can we lose?! I made some slight modifications to the processing of our test photo at www.perseus.gr/Astro-DSO-NGC-6913.htm which I hope you approve. If so, we can use the new and improved processing for our official entry shortly involving NGC 457 in Cas.

A couple of questions Anthony:
1. Why no flat?
2. Why 1:1:1 RGB ratio?
3. Where do the diffraction spikes come from?

Dave

A couple of questions Anthony:
1. Why no flat?

Unfortunately I am not an electronics guru ... in fact more like an ignoramus! I asked a friend who is quite active with electronics to construct me a light-box but he has dragged his feet quite a bit. I have asked another friend to get me the electronics only done but he is busy with a baby coming due shortly.

Yes, we have t-shirt and sky flats but I am not sold on them. The problem with flats is that they can do more damage than good if not taken properly.

2. Why 1:1:1 RGB ratio?

That is only for the exposures themselves. I weigh each of the master RGB files prior to constructing my master RGB using calibration results from a G2V star and which I describe fully at www.perseus.gr/Astro-Tips-G2V-Star-Calibr.htm . The weights I use are 1.531:1.000:1.279 for prime focus using the AP160. If any change is done to the optical train (ex. a 2x Barlow), the calibration must be redone.

3. Where do the diffraction spikes come from?

I used a couple of strings perpendicular to each other and attached to the dew shield. As a result, the horizontal/vertical spikes you see are due to this contraption. I expanded the spike pattern by adding another two spikes at 45-degree angles using Photoshop (there is a brush tool for this).

As for the latter - the artificial spikes - it is something that is very commonly employed by some of the biggest names in the world of astrophotography to great effect and is something which I like as well. A couple of people I have asked locally have expressed mixed feelings about the 'enhanced' spikes. Any thoughts?

I hear you on the flats - still, with your combination I'd assume that good flats would offer only a minor improvement.

The RGB article is very good!

As for the spikes - I'm really not sure. I'd have to see the image without the spikes to express a preference. That said, I think the spikes look good and give the image a sense of movement and life.

I think we're onto a winner

I'm monitoring this very closely...

:lol: :lol: :lol:

I'm monitoring this very closely...

To follow-up, Dave, the photo was taken with my Tasco 60mm refractor and at 675x during average seeing. A firm tripod allowed for the simultaneous mounting of my one-time use and throw away camera. The flash was used to produce the beautiful spikes around the brighter stars.