3 sessions in one day

[Paz]

I was down near the south coast at the weekend and took the ST80 in case any opportunities arose to do some observing. I was expecting permanent cloud cover but have learned to always be prepared. Saturday was a clear blue sky with the odd bit of wispy white cloud.

In the afternoon I got a half hour to look at the sun. This was with the ST80+AZ3 with an Orion solar filter strapped over the stopped down aperture – making for a 40mm f10 scope! No details were visible on the sun at all, I tried up to 80x with a 5mm SLV. I also tried a baader solar continuum filter but the solar filter lets orange/yellow through not broadband white light – so combining it with what is a sort of green filter left too little brightness getting through. I saw online later there was one small feature (2636) on the sun but I didn’t see it.

Nearer to sunset I was back out for a look at Venus. With Venus being the only target to look at I had a good time trying out various permutations of filters and stopping down the aperture. After some time I settled on stopped down to 40mm f10 again, with a semi-apo filter and a variable polarising filter which I tweaked to get the brightness that showed the best contrast. I spent the most time with the 2.5mm SLV at 160x and through trial and error managed to get a really good focus by trying many times to get the focus spot on and not settling for second best – I left the focus alone after this! The sky was still clear blue although not broad daylight but through the scope the sky was black with a really nice contrast Venus hanging in the blackness – not dim and not overbearing. After resetting the view and watching many transits across the FOV I noticed the shape of the crescent distorting a bit at the edge of the FOV. I am assuming the slight distortion I noticed was due to the eyepiece being deliberately designed to show stars sharp to the edge with the flip side of this compromise being the distortion of straight lines at the edge, but this is only from reading about it, I could be wrong (and it would not be the first time if I was!). I thought I could see the limb side looked brighter than the terminator side but no other detail.

After sunset I was back out for a general look around. I hopped from Venus to Comet 2P/Encke which I spotted in Sky Safari, but  having found the right spot it was not possible to see – I was looking low towards Southampton and the skyglow was very bad. At home I get better than NELM 4.5, sometimes close to 5 but here was worse than Magnitude 4 in the direction of Southampton!

Hopped back across to Mars – nothing to write home about here.

Hopped towards Uranus and noticed a nice double star on the way and stopped to check it out. This turned out to be Zeta Psc, wide (23.7”) and bright (magnitudes 5.2 and 6.3) so easy even in a small scope at low magnification.

Uranus seemed stellar – no size and no colour seen. Tried it up to the 5mm SLV (80x). I wondered if I had made an error and fixated on a star - but it looked like I had it according to Sky Safari.

Realised M31 was in sight – took a leap from beta Andromedae with the red dot finder and landed on it straight away. It was a small washed out core so I didn’t stop to look any further.

Decided to ditch low contrast targets and go for easy wins...M45! Very nice, blue, striking even at 12.5x and 4.2 degrees fov. Even better at 16x and 3.1 degrees fov. No nebulosity but none expected after seeing M31. It’s nice to see well framed – the big scope can’t fit any space around this to give the same context.

Caldwell 41 – too big to fit in – I was still at 16x and 3.1 degrees field of view. Different colours noticeable straight after M45 – more yellows. Theta 1 and 2 a nice double in a field of a lot of bright stars.

Collinder 65 – again too big to fit as I was too lazy to change eyepieces and was still at 16x. A distinctive pattern in the lower right quadrant was used to confirm where I was. This was field of fainter stars – no colours standing out, this cluster is much further away than M45 and C41.

Collinder 69 – another distant and faint cluster but with some brighter blue stars standing out (I think) in the foreground. I didn’t really notice the cluster - the foreground stars were striking. The best view was at 40x with the 10mm SLV.

I had a go at Lamda Orionis and got a very nice clean split at 160x with the 2.5mm SLV – this is a cheeky amount of magnification for this scope but it was doing fine. The clarity of it was a surprise and this target got the longest view of this session – although keeping an AZ3 on target at that magnification takes a bit of work.  As with Venus earlier I concentrated on getting a good focus which makes a big difference – focusing is not easy without a dual speed focuser.

I then had a look at M42 at 12.5X. The stars were nice but the nebula was small due to skyglow so I didn’t look for long.

I had a go at finding M44 but it's a harder find than things like M45, especially with lots of light pollution, and I find the AZ3 mount is not easy to balance/use at higher altitudes and so after a bit of faffing I gave up and quit while I was ahead.

All in this was a good day – the sun was a failure but Venus was an epic win, and in the evening Lamda Orionis was a great surprise I wasn’t expecting to look at or be able to see.

The ST80 did well – with getting the focus exactly right making a big difference (for me), and stopping it down to f10 really paying off sometimes.

The AZ3 is portable and it has been a good workhorse but the lack of natural altitude balancing makes for hard work when target altitudes vary.

My vixen SLV’s continue to grow on me – they are easy to use with good eye relief, small enough to take out in pockets, light enough to not cause balance issues, and give good quality views.

[cloudsweeper]

Great account of your sessions Paz - thanks for posting!

Doug.

[Stu]

An excellent day's observing! Venus is looking great at the moment, isn't it? I agree that the limb side does show brighter than the terminator side, I can't see much more than that in the Tak, other than a few subtle variations which may or may not be real! I much prefer observing it in twilight whilst it is still high in the sky, much better than the multi coloured, multi image result you get later on!

It may be worth trying a full aperture solar filter. At 40mm you do gain focal ratio but lose a lot of resolution. You may have picked up the spot with the full 80mm, worth a try anyway.

Sounds like your sky conditions were not that great later on, so well done for achieving all you did.

[laudropb]

Very nice report of productive sessions. I really enjoyed the read.

[kilix]

Nice report, I love reading these, especially when it is cloudy here and the writer has the same scope as I do!
You really pushed it hard with 160x, good to know that it is possible.

As for the alt balancing - have you tried some of the recommended DIY tweaks, like homemade counterweight or better alt locking nut?

[Paz]

14 hours ago, Stu said:

It may be worth trying a full aperture solar filter. At 40mm you do gain focal ratio but lose a lot of resolution. You may have picked up the spot with the full 80mm, worth a try anyway.

Yes I will keep an eye out on astroboot and abs. I've got a solar filter that fits the ST120 and MC-127 but couldn't think of an easy and safe contraption to attach it to the ST80.

9 hours ago, kilix said:

You really pushed it hard with 160x, good to know that it is possible.

As for the alt balancing - have you tried some of the recommended DIY tweaks, like homemade counterweight or better alt locking nut?

160x was working on this occasion but it's not always so. More usually 80x - 100x is the most I go with this scope - particularly if moon watching. On the moon I find floaters are more obvious than when looking at stars, and I find getting the focus just right is more elusive on the moon compared to on stars. With Venus I was concentrating on the pointy bit of the upper horn of the crescent for focusing which provides a helpful sharp shape that lets me know when all is good. 

I have read about some mods to the AZ3 but don't have the skills (and I am too lazy!) to have a go at them - rather I fantasize about getting a Vixen porta II mount or something like that!