Observation report 05/10/07 +04/10/07

[lunator]

Last night was clear and so as the make the most of it I decided to get a few double star observations and measurements in.

I started with Theta Serpens also know as STF2417.

They were an easy split in the 8" newt at x48 (25mm Ortho)

They appeared as two evenly matched white stars with a difference in magnitude of about 1/2.

This matches well with their A5 spectral class.

The field was pretty rich with more stars to the North than South.

There was a small asterism just to the North East that did remind me abit of Auriga in shape.

I took several measurements using the microguide & 3xbarlow and my preliminary results are PA 104.3 degrees. Separation 22.2".

My next target was Pi Aquila, again 2 evenly matched stars both yellow in colour.

I did make an effort to measure them but the seeing wasn't quite up to it so I decided to move on.

The next target was the other double-double not quite as famous as the Lyra pairs but still a great view.

The pair in question are gamma delphinius STF2727 and its nearby double STF2725.

Both pairs were able to fit into the 25mm field of view and could also be split into their components. Gamma was the easier to split of the pairs.

Both of the stars of Gamma appeared to have a yellow tint but the primary is a much warmer colour. This fits well with the spectral classes of K1IV & F7V at higher magnifications the secondary does lose a little of it colour and this is probably due to the increase in apparent separation, so reducing any impact of the primary has on the perception of the secondary colour.

The STF2725 is a closer pair and was a harder split at x48. The primary is an orange colour and the secondary although faint and showing no colour at first (grey? in my notes) did have a hint of orange occasionally. The primary is a K0 class star and the secondary based on Tycho info is a late G type.

The measurements for Gamma Del. are PA 268 degrees and separation 9.3".

The measurements for STF2735 are PA 10 degrees and separation 5.7"

The final target of the night was Epsilon (1) Equuleus.

This pair is another easy split in the 25mm Ortho. The field is also has a good scattering of faint background stars.

The primary appeared as a white/cream colour that is a reasonable match to its F6IV spectral class. The secondary did not show any colour as the high mist was beginning to make the transparency very poor. It clout index from Tycho is around the same class (F5-F6) so on a better night this should appear yellow/white.

The primary is a very close double (<0.7") and I was not able to split it but I could see it elongated east/west.

Cheers

Ian

[MartinB]

Phew! You must put a lot of preperation into your observing session Ian. Fascinating stuff

[lunator]

Hi Martin

To be honest this session was to just get back into a groove after a long period of clouds.........

All the targets are naked eye from a dark site so can be found easily in the finderscope. The time consuming bit is the measurements as you have to take several and each time the star has to drift across the FOV.

I deliberately stayed clear of faint neglected doubles as the transparancy would have made it a pretty thankless task.

Cheers

Ian

[lunator]

A did some follow up observations on all the doubles.

I added several measures to all the observed pairs and added Epsilon Equ.

I also took pics using the compact camera od the same pairs

I hope I have been able to catch STF2725 as it is quite faint.

I'll post what ever I have.

Cheers

Ian

I will have a look at the images this weekend.

The sky was quite clear at the start but