Asteroids in the moonlight

[iamjulian]

Set the scope up outside while I enjoyed a dangerously hot curry designed to keep my warm later. To be honest the scope didn't need much cooling down time as the garage was also freezing cold. I had Cartes du Ciel on by the back door to help me locate targets, knowing the moon was too bright to worry too much about dark adaptation. 6.30pm. Spent the first few minutes having a look around, seeing which constellations were visible and what to aim for. Decided it was an asteroid night. First target 19 Fortuna, mag 9.6, located between Aldabaran and Zeta Tauri. I found a useful line of 5 stars from which to hop from. But the area that should have contained the asteroid and a couple of other stars wasn't yielding anything. The blackness was more pale grey, the moon was obviously going to cause me more problems than I anticipated.

There weren't many brighter asteroids in the area of sky that I could observe, so I half gave up on asteroids and moved up to Aldabaran and the Haydes. So pretty. I found two stars quite close together, one white, and one yellow. Up until now I had been using the 32mm EP (24x), but switched to the 6mm (125x). And that's when the obvious struck me. The light gathering power of the 32mm was sucking up so much moonlight that it was overpowering the fainter stars. With the 6mm, while looking at my white and yellow star (CdC called them The1 Tauri and The2 Tauri) I could see a couple of nearby stars that were mag 10.6. As luck would have it, asteroid 346 Hermentaria at mag 10.5 was sitting almost between my white and yellow star. Fantastic! Back to 19 Fortuna and I was soon able to star hop to my target at 125x magnification.

I stood back for a moment to have another scan of the horizon and was delighted to get my first view of the top of Orion, arms raised above the horizon. But I was on an asteroid roll now and popped back indoors to see whether there were any more in range. I have seen 89 Julia before but it has moved below Alpheratz now, though still close enough to be able to hop to so I couldn't resist revisiting this lump of rock, before heading south in search of 3 Juno. Long story short, I couldn't find it before that section of sky slipped behind a house.

9pm I was getting cold now and wanted to head indoors, but Orion was awake and it would have been foolish not to turn the scope on M42 for my first telescope view of it. Even in a very moonlit sky it was impressive and I cannot wait to view it properly. It was a great night and I didn't even look at the moon.

[skye at night]

Hello,

Interesting set of targets for a cold evening...

It got to -6 overnight here according to our outdoor sensor.

I think i would have managed a run of asteroids () if I'd sat out there for long!!!

Steve

[Doc]

Having never hunted asteroids before can you tell me if you can see these move in your fov pretty quick or do you have to sit for ages looking for movement

Lovely report and very interesting.

[iamjulian]

ha ha, good one Steve.

Doc, you cannot see them move, well certainly not main belt asteroids. I'm not yet very good with descriptions like arc minutes and all that, but you can see them move night to night. But not while you are looking through the EP. Maybe around one degree per week as a very rough estimate!?

A nice speed to pick them up on widefield photography if you get a couple of clear nights in the same week. Earlier in the year I managed this one of Ceres on 3 consecutive nights:

[Doc]

Thanks for the reply. I was hoping to see them move... Doh what a noob

I suppose you can always sketch the stars if you haven't got any cameras.

[Talitha]

Great report and pics, Julian! Btw, i love this part of your signature: "4/14971 named asteroids seen".

Now that's what i call optimism!

Also wanted to say that M42 holds up surprisingly well to lunar interference. Recently, i sketched it on a moonlit night and then went back again to complete the sketch when the Moon wasn't a factor. It was surprising to see how very little i was able to add to the sketch on the completely dark night.. just some dimmer stars and a bit more outer nebulosity (no filter was used on either night).

Mick, try comets if you'd like to be able to see something move. When fragment C of Comet 73P/Schwassmann-Wachmann sailed past M57 (8 May 2006) i could easily detect the movement against the starfield within 10-15 minutes... very cool.

[skye at night]

Like comets in a way..

it is spotting asteroids and finding that they move over day to day-week to week.... that identifies them..

and that generally is how they are discovered...

Clyde Tombaugh, knowing that there was another 'object' out there (due to wobbles in Neptune and Uranus' orbits (don't hold me to that) used his 'blink' type photo comparison over time to identify Pluto....

There are still comets and asteroids/planetoids out there to be discovered.. as long as the automated surveys can be beaten to it though...

Steve

[iamjulian]

I'm only looking for the ones marked in Cartes du Ciel, I have no ambitions to find anything new, not with my scope anyway Like you say Steve, the big survey scopes like WISE are due to find a few hundred thousand more.

Carol, got to have a goal I'm not sure how many of the near 15,000 will be visible to my scope, maybe only a couple of dozen but I'll try to bag as many as I can visually, then I'll have access to plenty more if I start imaging.

[pvaz]

Seams like you had a great night.

Very interesting choice of objects. I'm a bit fixated on DSOs and planets but I'll try picking a couple of comets for my next observing session.

[Phil Fargaze]

I would be interested to be able to get images of asteroids like your example of Ceres (once I get myself an eq mount) but was wondering if you would reveal what camera you used.

[iamjulian]

I have a canon 400D. That Ceres photo was taken before I had my telescope/mount, on a really badly made barn door mount - two bits of wood, a camera ball head tripod bolted to the top one, a basic door hinge joining them together and a standard bolt with a wing nut to push the top board. Each night I took four exposures of about 1 minute each and just picked the one with the least trailing. I didn't know about stacking at the time. It was a nice wide 30mm lens. Probably something like ISO800 and f/4. The brightest asteroids are about mag 7 or 8, so you only need a few seconds exposure before they show up. Let me know how you get on.

[Phil Fargaze]

Great, thanks for the info. Really good results for a simple set up!