December Star Hops To Galaxies

[Mr Q]

Before we start, just a reminder for those with extended cloudy periods - if you are one, write down these hops for later clear periods or for reference next year.

The most important requirement in star hopping is knowing your field of view size in degrees. To obtain this, choose a LP EP that you will be using to locate the objects. Next, pick a fairly bright star from -10 degrees to +10 degrees DEC along the celestial equator (0 degrees DEC). Place the star at just outside your FOV and time its passage across the FOV, making sure it passes through your FOV's center without moving the scope. Take that time in seconds and divide by 240 to calculate your FOV in degrees for that EP. Now you will know just how far your hops will be from the pilot star given in the hops as I give the distances in degrees.

This star hop session will require at least a 6" objective (or mirror) with fairly dark skies (visual limiting magnitude from about 4th to 5th magnitude near the zenith) to detect these fairly faint galaxies.

PEGASUS

Hop #1 Pilot star Eta Peg(4th mag.)

1. Move 4 degrees NNW to EG NGC 7331 (9th mag.) This galaxy is the brightest of several in an area of 3 degrees around 7331.

Hop #2 Pilot star Pi Peg (5th mag.)

1. Move 1 3/4 degrees SSW to EG NGC 7217 (10th mag.). An 8th mag. star lies 1/3 degree to its SW.

Hop #3 Pilot star Algenib Peg (4th mag.)(lower left corner star in the "square").

1. Move 2 1/2 degrees to the NW to EG NGC 7814 (11th mag.). A 7th mag. star lies 1/4 degree to its NW.

Hop #4 Pilot star Alpha Peg (3rd mag.) (the upper left corner star of the "square")

1. Move 3 degrees S to EG NGC 23 (12th mag.) A 13th mag EG (NGC 26) lies 1/8th degree to its SW.

2. Move 1 1/2 degrees S of the same pilot star to EG NGC 16 (12th mag.) A 6th mag. star lies 1/2 degree N of NGC 16

PERSEUS

Hop #1 Pilot star Sigma Per (4th mag.)

1. Move 5 degrees W to EG NGC 1023 (9.5 mag.) or move 4 degrees S of OC M34

ANDROMEDA

Hop #1 Pilot star Gamma And (4th mag.)

1. Move 3 1/2 degrees E to EG NGC 891 (10th mag.) A 6th mag. star lies 1/2 degree to the SE of 891.

Hop #2 Pilot star Beta And (3rd mag.)

1. Move Beta And just outside your FOV from the SE edge. EG NGC 404 (10th mag.) will lie just inside your SE edge of your FOV.

ARIES

Hop #1 Pilot star Gamma Ari (4th mag.)

1. Move 1 1/2 degrees to the SE to EG NGC 772 (10th mag.) A 13th mag. EG (NGC 770) lies next to 772 to its SE.

Have fun hunting these faint, challenging galaxies

[NGC 1502]

Agreed, for us manual star hoppers, we need to know how much sky can be seen through the eyepiece (actual field of view). The method Mr Q has outlined is called 'drift testing'. I've tried this myself, to find out if the indoor method of calculating this works. The indoor method is to divide the apparent field of the eyepiece by the magnification produced when used with any given telescope - for instance my 10" Dob is 1200mm focal length, and when I use my 27mm eyepiece I get 44x mag (1200/27 = 44). The apparent field of the EP is 68 degrees, 68/44 = 1.5 degrees actual field of view (about 3 moon diameters).

When comparing this method with drift testing, I've found that both give very similar results (good enough for me) for successful star hopping.

Another method uses the field stop diameter, but I've never tried that, but I'm sure it works as it's well documented by top eyepiece manufacturers.

I do use the actual field of view method outlined in post #1, but more often look at where the object is on my star maps (S&T pocket sky atlas or SkyAtlas 2000) relative to naked eye stars, put my red dot finder on that bit of sky and look into the EP, if the object cannot be seen, pan around a bit, and usually the object is found. I can then shift to the EP that gives the best view.

When using my 70mm refractor, my 27mm EP gives 17x and 3.8 degrees true field, so it's easy to find many brighter DSOs, even from a light polluted site.

I'm very definitely not against using go-to, whatever gets you under the stars and works for you is good

Regards, Ed.

[Mr Q]

Ed- Thanks for the info. I always wondered what, if any, difference there was between the drift method and the math method. Iv'e always used the drift method and from your post, I see there is not much difference despite what the experts say. I have taken the drift method further in observing to get a rough idea of any one object's size by doing the measurement with a HP EP and what I found was close to the published size. Most of the difference I'm sure is the published photographic size vs the observed size but for small galaxies and other objects, the two are fairly close.

To help remember the drift method, I use "crossing time in seconds divided by 240 seconds" and except for some distortions at the very edge of the LP EP, the measured size is close enough for hopping use as well as observing notes as to size of an object seen.

[Double Kick Drum]

That's a great guide to some of the galaxies which are currently at their best.

With the exception of NGCs 16, 23, 26 and 770, I have spotted them all with a five inch refractor. Most of them in the last three months or so.

A great example for beginners / intermediates setting their sights on more difficult galaxies is NGC 404 (the Ghost of Mirach) which is a doddle to locate but reasonably testing to see beyond the glow of Mirach. It gives an idea of how subtle a smudge some of these DSOs can be.

NGC 1023 in Perseus is the other way round. A very bright condensed galaxy which can get lost in the rich star fields in that area.

Thanks for sharing!

[crazyjedi]

If I ever get a clear sky I will give this a try. Cheers

[Mr Q]

In the near future I'll be posting other challenging star hops in the "Observing-Deep Sky" forum with easier ones in "Getting Started With Observing" I got the info and experience, all you need is the clear skies