Highest mag my ToUcam can see

[astrodave]

(1 of 6)

Some months ago having just taken delivery of my ToUcam, one of the first questions to cross my mind was - "Unmodified - what's the highest magnitute star I can see?"

I set out to see - which led my through quite a journey as I am about to relate.

First with my 10" - f4.5 the ToUcam was seeing about 11' x 8.25' of the sky. How could I know where I was (the days before my DSC) and capture dim stars? I chose the region around gacrux - the "top" star of the Southern Cross. Here I could see gacrux and a number of dim stars around it.

Here's the image (around 1500 frames stacked) with some of the stars identified.

Okay - how did I identify the stars......

[astrodave]

(2 of 6)

How to identify the stars? I turned to my newly acquired Stary Night Pro 4.5 ...

But it didn't help me much (catalog based on Hipparcos & Tycho-2). That's okay I thought - Stary Night has an online feature where you can download extra stars for a region from the USNO B catalog.

The image from Stary Night below (JNow) has the USNO stars added in. But my little ToUcam image has many more stars than are listed - what's going on.

[astrodave]

(3 of 6)

The US Naval Observatory has a web site where you can query the contents of their catalog and get Finder charts and even images from which their catalogs were built. (www.nofs.navy.mil)
[Don't you love broadband..]

So I get a finder chart (based on USNO B) for the gacrux region (image below). But, it has a halo of nearly blank space around gacrux - where I can see stars!

Can I see stars that the US Navy cannot? - I don't think so...

[astrodave]

(4 of 6)

The USNO will drag images out of their archives if you wait 20 minutes or so. So I want to know why there is a halo of nothing, so I ask for some images... A rather overexposed gacrux blots out all the nearby stars.

So the catalogs are missing stars because the routine survey images overexpose bright stars??? Has anybody else noticed this? Am I missing something here? Is there another explaination?

[astrodave]

(5 of 6)

In writing this journey up for you guys I went back to the USNO web sit to get some details. I then discovered that they issued another catalog in Nov '04 - NOMAD. So I had to ask it about gacrux...

The situation is a little better - but there are still some stars missing...

[astrodave]

(6 of 6)

How dim can my ToUcam see? Well I gave up on gacrux and went to the Jewel Box instead.

I reckon I've identifed a 14.5 mag star ...

(Suburban Melbourne, 500 stacked frames, 10" f4.5 Newt, ToUcam at Prime Focus)

[Orion]

You must have a lot of time on your hands Dave, It's all very impressive! I did not know the ToUcam could go that deep.

[Mombat]

Next stop pluto! I think the most impressiven part is actually recognising the stars i have no where near enought patience to do thast

[[1ponders]]

Good onya Dave. Don't you just love researching stuff just for the fun of it. :) And then sharing it around. Its what learning is all about. Top stuff!!