#### Observing Project Assessment - 20% of total

As part of PHY241, you will be expected to complete a simple observing project using the 16-inch telescope on the roof of the Hicks Building. This project is designed to give you basic hands-on experience of astronomical observing and data reduction, and can be completed in a few hours of telescope time. The observing must be done in groups of up to seven students. You must sign up to a group on Blackboard by the end of week 1 Friday 30 September 2022. If you do not, I will assign people into groups at random.

There are three aspects to the observing project.

Planning

Well before your scheduled observing run, you choose which open cluster to observe. You will find the specifications of the Hicks Observatory useful in your planning and when writing your report. You will need to include a section on your planning in the final report. This section must contain a calculation of the transit time and the transit altitude of your chosen object. You may find the positional astronomy notes from PHY127 of use.

A suitable open cluster must be:

• old enough so that some stars have turned off the main sequence;
• close by, so that the stars that have turned off the main sequence are bright enough to observe with the 16-inch telescope from Sheffield;
• small enough in anguilar size to fit within the field of view of the 16-inch telescope with the focal reducer;
• visible from Sheffield in the months of October and November.

I give more detail about these points below.

Age

Brightness

This course will teach you the skills you would need to put a quantitative number on this, but for now, just know that you want the stars at the main sequence turn off point to have a V-band brightness of V < 13 to 14.

Note that you will often see the integrated magnitude of all the stars given for the cluster. This is how bright the cluster would appear if you couldn't resolve individual stars - you don't want to use this magnitude to make decisions about the brightness of stars at the main sequence turn-off!

Size

You can find the field-of-view of the Hicks observatory in the specifications. The cluster should fit within this.

A list of potentially suitable open clusters are listed below; select one from this list before you observe, and email Stuart Littlefair and Paul Kerry to inform them of your group number and cluster choice. If you wish to observe a different open cluster, that is fine, as long as it meets the criteria above.

#### NGC 7789

• $$\alpha$$ = 23:57:24
• $$\delta$$ = +56:42:30
• Turn off @ $$V \sim 13$$
• $$D \sim 16'$$

#### M67

• $$\alpha$$ = 08:51:18
• $$\delta$$ = +11:48:00
• Turn off @ $$V \sim 12$$
• $$D \sim 20'$$

#### NGC 6939

• $$\alpha$$ = 20:31:30
• $$\delta$$ = +60:39:42
• Turn off @ $$V \sim 13$$
• $$D \sim 7'$$

#### NGC 2627

• $$\alpha$$ = 08:37:15
• $$\delta$$ = +-29:57:18
• Turn off @ $$V \sim 12$$
• $$D \sim 10'$$
Observing

Your observing session will be remote, via Blackboard Collaborate or Google Meet, and will be supervised by Paul Kerry or Stuart Littlefair. It must be completed in a specified period: Mon 10 October - Friday, 09 November 2022 (weeks 3-7), although please note that observing is not possible over weekends and there may be short periods when either myself or Paul Kerry is unavailable.