While not my specific plan, being in the back garden, in the dark with a telescope is a very effective way to miss the little beggars knocking at the front door.
I have fairly limited sky views at my home and so using an old fashioned £5 Philip’s planisphere that afternoon I had made a list of possible targets and times that pass across the ‘viewing slot’ – a gap between the Methodist church next door and my house wall, a width of about 25°or 1.5 hours RA at an elevation of 25°. One of my current personal projects at the moment is to work though the BAA’s 100 double star list and send my readings in to the BAA with my estimates of separation. The section leader has derived a method of measuring that only requires a stopwatch, but that is another story. Tonight I was just planning on using my Celestron illuminated reticule. A long focal length / high magnification is best for this task. The 200mm C8/F10 is my normal instrument for this work but, being a bit old, it has no go-to option or any possibility of fitting such things to the mount (but it does have digital setting circles, the next best thing). So, my weapon of choice tonight is the little Vixen 110mm on the Sky-watcher Alt Az go-to mount. This was my first try with it connected into the laptop computer (yet another story). I am using the same free software as we use on the LAS telescope, ‘Cartes du Ciel’. While the Skywatcher go-to hand control is OK, it is a bit of a pain having to pre-load the RA/DEC of stars not already in it’s limited list of double stars as ‘user objects’ hence trying this new configuration.
18:00 γ Del. was found easily and measured as 9.8” / 270° when compared to ‘reference standard’ of 9.1” at PA 266°. All in all, I am content with that 0.7” / 4° error. This was first double star I ever saw at the age of about 11 or 12 with a little 60mm cardboard tube telescope on homemade Meccano mount, while hanging out from a tenement window in Glasgow. I had seen pictures in of it in my ‘Observers Book of Astronomy’ but it was that night many moons ago I realized stars really did have colour.
18:30 M15 was easily found by the mount + planisphere software combination, but I not able to resolve any stars.
ε Peg. – measured the ‘b’ companion was very faint. Anyway my estimate was recorded as 158” an error of 14” against expected value, but my PA of 317° was only 1° away from the ‘book’ value of 318°. As this was a wide double I could only take a single reading without a Barlow. This is where the ‘stopwatch method’ may win.
18:55 Quick look at M2, while in the area. No detail, just a fuzzy object. Double star 94 Aqr was too low behind the church at this time made a note to came back to it.
19:47 η Peg (Matar, β1144) This 110mm scope should pick up its 10th mag ‘b’ star OK (‘Norton’s’ says 100mm limit is magnitude 12.7) but sky was a bit ‘milky’. I had set up the Sky-watcher Explorer 130mm on the Vixen GP equatorial mount (not a go-to, just plain German equatorial mount with motor drives) so finding the same star by telrad finder I could just see the companion but measurement was not feasible.
20:58 Back on the Vixen 110mm I found ‘Blue Snowball’ NGC7662 using 9.5mm (x100). It is next to 13 Andromeda and I used κ and ι to check computer and the mount synchronized. In this nights sky it was not stunning, but even with a small scope there was a hint of blue to be seen.
Now the big mistake of the evening. To get a better view of my fuzzy I replaced the relatively light-weight Vixen 110mm with the Explorer 130mm on the go-to mount. Just because it fits is no guarantee it ‘works’. This is a ‘short’ tube F5 telescope however it is still longer and a bit heavier than the Vixen and the longer tube snagged on the mount leg. So knocking out all the set-up calibration. So after setting-up again I tried to find M32 – the sky too bright. Then 94 Aqr – but I had missed my window of opportunity as it is now ‘in the house wall’. Now, in an effort to see at higher elevations without snagging the leg I had pushed the Explorer 130 up a quite a bit in the dovetail saddle but as a consequence the mount was unbalanced and struggling to track or find objects, so I put the Vixen back on. Lesson learned.
22:38 Uranus observed. The advantage of the direct link to programs like ‘Cartes du Ciel’ is it shows the observer what else is in the whole sky area where I am pointing the ‘scope. Using 9.5mm (x100) eyepiece it is a small blue/green disk, clearly not a star. At x200 the image was blurry on this night so I found tonight a 12.5mm + x2 Barlow (x160) gave the best view.
22:53 Next I slewed under computer control to α Ari (Hamel) for a computer to mount sync check then on to double star λ Ari. Measured it at a separation 39.5” and PA 50° compared to reference of 36.7” at PA 47°. Next I observed ε but could not resolve it at 1.4” with this 110mm telescope (the resolution limit for any amateur telescope is about 1” due to our atmosphere) . Moved to the “Rams Eyes”, γ Ari measured its separation only as 9.3” compared to 7.5”. Noted in my book however the PA orientation was by eye N/S i.e. one ‘on top’ of the other.
By now the moonlight, dew and a low mist forming was making seeing even worse and was becoming a problem so I called it a night.