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12" Dob First Light

Davesellars

By Davesellars
in Observing - Reports

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Davesellars

Davesellars

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OK...  So after pretty much one month after getting the 12" Flextube Dob I get to use it on some DSOs.  The forecast was OK but also for fog rolling in.  I took the chance and lugged myself out with a whole bunch of gear for the first time.

Setting up was at least reasonably quick and aligning the RACI to the Telrad (which had been aligned previously to the scope) and then checking the primary collimation (very quick using the Cheshire!) I was good to go.

I could see plenty of stars but there was indeed loads of humidity the dew attacking everything pretty much as I was setting up  - not a good start.  Fortunately I'd built a full dew shield from some 3mm foam which worked a treat otherwise I think I'd have been dead after a mere half hour on the secondary mirror.   Still, I'm wondering if it's worth getting a Kendrick dew ring for the secondary for longer sessions or just get a 12V hair-dryer to blast it as required to clear dew.

So... First DSO!  It had to be M13.  To start off I wasn't using the Paracorr wanting to see how it performed without it.  The scope since it's kept in a shed was already pretty much at ambient temperature and so zero cool down seemed to be required.  Stars were sharp from the get-go!  I loaded in the 24mm and pointed at M13 which showed a lovely mass of pin-point stars right through to the core.  Straight to the 11mm the contrast improved dramatically and M13 showed wonderfully bright - a mass of stars resolved deep to the core.  Wonderful!

Swinging over to M31 popped in the 19mm Panoptic.   Very faint dust lanes just about visible away from the core occasionally as the transparecny wafted in and out. What struck me most was how bright and large M32 looked!   The stellar centre of M31 easily resolved and a considerably large core.  M110 was almost too easy given the conditions this may not have been visible with the C8.

With the altitude of M31 at this time I did find it a little difficult to move the dob accurately though.

I moved back over  to the West to M57 and popped in the 14mm Delos.  Bright and showing some structure in the ring and the oblong shape.  No colour coming through but perfect with less magnification.

Fog was rolling in an out... My RACI and its eyepece had dewed over so I put on the dew system.  Noticed the wire to the 4" dew strip was getting very hot so pulled it out and replaced with my 8" one.  Will have to fix later I assume it's shorting somewhere. 

While the dew system was doing its stuff I had a look at The Pleiades - Nice but much better with the small refractor or bins.

On to the Double Cluster which I could just make out naked eye so plonked my Telrad on it (made a dew shield for this as well which was just about working sufficiently not to knock it out of use completely from the encroaching dew monster).    Then I had to pick up my jaw up from the ground.  Man, there is so many stars in that cluster.  In fact one thing about much more aperture was how many more stars and how much brighter everything was.  Lovely colour in the two clusters as well.  The 14mm Delos did a great job but needing to concentrate on one cluster at a time.

While I was on the double cluster I installed my TV Paracorr and with the same eyepiece made a comparison.  Yep, the stars are definitely tighter and sharper across the entire field.  However, I'd have been perfectly happy without the Paracorr at this point although I hadn't tried that many EPs  The 24mm, 19mm pan and 14mm Delos certainly gave excellent performance to the edge without the Paracorr - certainly considerably sharper than my C8 but not at the sharpness level of my ED refractor.  With the Paracorr installed optically it was getting pretty close to refractor tightness.  Perhaps though for really faint DSO hunting I'd leave off the Paracorr - It will be interesting to test on another night with an at-the-edge of view DSO to see if the Paracorr detracts at all.

My finder had just about become usable again so onto Pegasus and NGC 7331 - I found this easily enough.   It showed a brilliant core and an interesting shape with a slight central bulge. Very obvious the slant of the spiral galaxy and nice to see a small amount of structure outside the core.

I had a look for Stephans Quintet but I had a bit of trouble and failed to look in the correct direction (doh!  yes Newts are all flipped I keep forgetting... :p)

I made an attempt for a new object on the H400 list only for clouds to roll in somewhat sooner than expected...  So that was it!   While packing up I shone the light in the focuser to check the secondary - it was dewing up - hardly surprising really.  The primary also had a bit of dew on it but nowhere near as bad.

Rather mercifully I found it very quick to pack everything away.  Next time at least I should be a bit more organised!

So...  I'm impressed!  The 12" dob has great optics it seems - Really sharp and bright and good star colour coming through.  Given the conditions also the extra aperture certainly seemed to make a huge difference over my 8".  Now I need to wait for a much better evening for some really faint stuff!

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Stu

Stu

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Dave, I'm replying to this so I can have a proper read of your report later. All sounds excellent so far though, nice one!

Im hoping to have a similar experience this weekend with my VX12L at Lucksall.

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niallk

niallk

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Great stuff :thumbsup:

It's a constant battle against dew for me too most nights!

I found that too: star colour, brightness and the sheer number of stars is so noticeable with increased aperture. Globs respond remarkably well!

Hope you get a run of good weather now around new moons to enjoy DSOs in all their glory :)

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Davesellars

Davesellars

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19 minutes ago, cloudsweeper said:

Great report, Dave - and especially encouraging for me since I'm planning on getting a 300P Flextube next!

Doug.

You'll not regret it!  They are pretty solid but easy to move imho. Although I don't have to carry it far I carry the base out first then the OTA.  The azimuth movement is really smooth. In fact i tightened it up a touch to avoid it hanging EPs.  Altitude balance is a challenge ATM but I load it with a Telrad and a 60mm RACI as well as having replaced the focuser with the rather heavier dual speed Moonlite.

As far as views goes it is a considerable difference to the 8" SCT I had (which was no slouch itself!).

 

 

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cloudsweeper

cloudsweeper

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47 minutes ago, Davesellars said:

You'll not regret it!  They are pretty solid but easy to move imho. Although I don't have to carry it far I carry the base out first then the OTA.  The azimuth movement is really smooth. In fact i tightened it up a touch to avoid it hanging EPs.  Altitude balance is a challenge ATM but I load it with a Telrad and a 60mm RACI as well as having replaced the focuser with the rather heavier dual speed Moonlite.

As far as views goes it is a considerable difference to the 8" SCT I had (which was no slouch itself!).

 

 

Yes Dave, I noticed the absence of the SCT.  Can't wait to do a comparison for myself.  (It might take a while before the next acquisition though!)

Doug.

 

 

 

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brantuk

brantuk

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Smashing report - I agree with all the above - my SW 12" flextube was a fine instrument and gave me great views of everything. I only let it go cos I eventually succumbed to aperture fever and upgraded to 16". Eventually I'll self build a 20". Have fun with it. :)

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Davesellars

Davesellars

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19 minutes ago, chiltonstar said:

A nice report! Certainly was a lot of dew, wasn't there - I had a puddle in the centre of my front corrector by the time I had finished early this morning.

Chris

:shocked:  You made it through to early morning!  Clouds came through pretty thickly at about 11 (or just before) here so well done for sticking with it despite the dew!   I think I've only been out once before when it's been so bad with dew when my C8 lasted 30 mins and the dew system couldn't keep up and my binoculars dewed up in 30 seconds! :p  Sometime you just can't fight against it. :p

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Davesellars

Davesellars

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1 hour ago, cloudsweeper said:

Yes Dave, I noticed the absence of the SCT.  Can't wait to do a comparison for myself.  (It might take a while before the next acquisition though!)

I couldn't see myself really using the 8" SCT when I have more aperture which is why I sold it.  I have my refractors for portability and perhaps for quick sessions. :) 

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cloudsweeper

cloudsweeper

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21 minutes ago, Davesellars said:

I couldn't see myself really using the 8" SCT when I have more aperture which is why I sold it.  I have my refractors for portability and perhaps for quick sessions. :) 

I suppose when I eventually get the Dob I might hang on to the SCT for:

# Very high mag without Barlows.

# GoTo, which I really like (sometimes).

Doug.

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Davesellars

Davesellars

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Thanks for the great comments everyone!

It was nice to get this session over and done with.  I've got some niggles to iron out mainly in balancing the scope well on the altitude axis as this shifts considerably depending on the altitude you're at.  I was using some wrist weight bands of 1kg and 0.5 kg which worked OK just sitting them on the top of the tube above the mirror.  Not sure if I get a better system going perhaps having the weight hanging below the tube.  I found I needed more weight than I had on the night (so will take with me next time the other 1kg weight) to view below 30 degrees approx with the Paracorr on adding more weight to the front.  It's a bit of a pain having to add / take off weights but generally I wouldn't be shifting about the sky quite so much.  What do other people do?

I'm sure once I've got used to the movement of the dob I'll be fine... :)

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John

John

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Great report Dave !

My 12" dob is still my most used scope despite the posh fracs that I've recently acquired. When the conditions are decent a good 12" can really dig deep into the sky and produce stunning planetary and lunar viewing too :icon_biggrin:

I find that I need quite a bit of weight on the back end of the scope when I'm using heavy eyepieces - most of mine are heavy ! :rolleyes2:

I have 2 weights which I can put in 2 positions on the lower section of the tube to vary the counterweight effect. I've sort of got to know what combination works and as the scope nose dips I usually need to up the weight a bit.

 

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Davesellars

Davesellars

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Thanks John!  Yeah at the moment it's a bit of trial and error.

I'm wondering if making a shroud from heavier foam will help.  I'll keep the Astrozap on permanently but if I could also wrap around a decent foam shroud around this I'm sure it would help significantly avoid the temperature falling in the tube too much and dewing up secondary and primary.  I guess solid tube dob owners don't have so much this issue...

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John

John

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26 minutes ago, swamp thing said:

Dave

To help balance I put one of those long magnetic knife racks on my small dob. That way one can simply place plate weights on it then slide them about to achieve balance, simples :) 

HTH 

Yep, thats what I've done too :icon_biggrin:

I found I needed to add a couple of screws through the rack to stop the weights sliding when the scope was pointing above a certain point but basically the same approach.

I don't get dewing issues with my solid tube dob, at either end, but that may be to do with my observing location being not dew prone rather than the scope.

I don't use a coma corrector with mine BTW but it's F/5.3 so coma is reduced compared fo F/4.9.

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