First light - Sky-Watcher Stargate 500p 20" GOTO Dobsonian

[Ships and Stars]

Hi all, first light and first impressions with the big Stargate 20” dob. This was definitely a milestone event for me with such a big scope, albeit short-lived due to fatigue and cold, and work early the next morning.

Disclaimer – I am new to astronomy, this is my first telescope in over 35 years since I had a little Tasco 60mm, which I used twice until the focuser fell apart. For what it's worth, I do have an extensive DSLR background and have done some binocular astronomy which has helped things a little. I love binos, but hankered for something powerful to view DSOs with, without the hassle of imaging complications. I’ve spent the past three months reading about telescopes and gear before settling on this dobsonian when one came up for the right price. Of course, I still have a LOT to learn, both about identifying objects in the night sky, and equipment. The good people here have already helped me out considerably. Thank you!

I did my first ever collimation yesterday afternoon using the supplied SW eyepiece. The secondary was rotated about 20deg off, simple fix once I realised why I was staring at the trusses through the pinhole eyepiece, and not the mirror!

I didn’t fiddle with the grub screws for the secondary. The primary mirror collimation took a bit of adjusting since it was removed from the rockerbox on arrival. I had to crank down the spring loaded-collimation knobs more than anticipated so the springs were almost fully compressed. Took about ten to fifteen minutes, relatively painless. I reckon I could always fine tune in the field.

Last night’s ‘mission’ was to simply check collimation and focus, run through night assembly, and then randomly sweep the sky without GOTO or gizmos and hopefully relax and enjoy the views, and then get a few hours' sleep.  

After the family was in bed last night after 10pm, I loaded the Stargate into my van and headed to a nearby forestry car park under Bortle 3 skies. Split down into four component parts, base with GOTO drive, rockerbox with mirror, truss rods and top end, it’s quite easy to shift for someone in reasonable health (my back is a bit dodgy, but I was fine). Moving the massive mirror/rockerbox is always a little stressful for me, just make sure the area is clear of trip hazards, check the base is ready to accept it, firm grip, focus and lift away…

It was quite clear but COLD last night, much colder than I expected, around -2C onsite. My body was well insulated with wool trousers and down parka, but my hands were going partially numb quite quickly, and heavy frost had started to form within minutes of parking up.

Set up of the rockerbox/mirror onto the base and assembly of the trusses was fast, even in the dark with a LED torch set to one lumen firefly mode. The top end with focuser took a little persuasion but clicked right in eventually. The truss clamps were more troublesome in the dark, I’ll be buying glow tape or something to ID the tops and clamp locations on the truss rods.

By this time, the frost was growing thick and the plastic flexy mirror cover already had frost/dew on it before I could remove it. I was exhaling clouds of moisture onto everything from the race to assemble. Not a good omen!!

I quickly attempted to put the dew shroud around the frame properly, but gave up with numb hands and tossed it over the scope like a blanket and roughly attached the ends so it didn’t obstruct the mirror etc.  I wouldn’t be observing at zenith because I didn't bring steps,  so no big deal. Job done.

I didn't bother with setting up the GOTO alignment and left my finderscope at home, so I just planned on slewing around and taking a casual look.

I removed the mirror covers, popped in the 28mm 2” SW eyepiece, took a deep breath, and…couldn’t focus. Brain engaging for a second, I popped the extension tube in place. I tried again with a spin of the focuser wheel. Stars of all magnitudes filled the eyepiece!

I had little idea what objects I was looking at, but I saw so many star clusters and double or triple star formations, while a few satellites zipped across the eyepiece.

I was delighted to get everything in focus with the 28mm 2" – it seems like a wonderful eyepiece for the money. Yes some coma as expected, but not bothersome to me at all.

Just for laughs, I swung towards the crescent moon before it dropped below the horizon and hunted for it until suddenly a huge flash hit my eye. Ouch! I was blown away by the intensity through the 20" mirror – I felt like I needed a welding mask to even quickly look at it. I couldn't look for more than a few seconds due to the intensity (my ND filer arrived this morning). I stepped away from the eyepiece and looked down at my parka – a bright crescent moon was projected across my chest! Not wanting to risk eye damage, I had one last peek with the 28mm and went for the SW 10mm to hopefully dim it a wee bit.

I popped the 10mm eyepiece in and got some incredibly close views, but the mirror had not sufficiently cooled for sharp focus.

Nevertheless, I can assure you I have never seen the moon in such detail, absolutely breathtaking!

Suddenly, nothing seemed to focus well. A quick inspection revealed my secondary mirror was c.60-75% covered in frost, so I fired up the heater in my van about 50m away, whipped the mirror off with a screwdriver (mind the spring underneath!), and warmed the mirror until the frost was cleared, all in the dark, happy days!

I reinstalled the secondary at the same index prior to removal, and all seemed fine. After that, the secondary mirror and primary remained crystal clear the rest of the night, but by this time I was cold and growing a little tired.

I don't know what magnitude I was seeing down to with the 500p but the light gathering ability is absolutely immense! It is an astonishing scope by my novice standards, and I'm sure I have barely scratched the surface.

Although this is a huge scope, you definitely don’t need one like this to have a lot of fun and enjoyment, so don’t sell the jewels just yet. I'm glad I kept my observation binos for times when I can't lug this scope around, and the appeal of a smaller, more portable dob in the future is still there. Last night would have been an equally great night with either of those as well. One thing I can say is you do NOT need a 20" dob to view the moon ?.

When I get time to set up before dark for a couple of nights in one spot, get the GOTO aligned, appropriate filters in place, and can target DSOs, etc then the 20" will make more sense and see more of its potential in use. Still, the 500p revealed a ridiculous number of stars with standard eyepieces, no coma corrector and rough collimation. A definite light bucket as they say.

So job done, got to quickly see some stars, nothing broken thank the gods, and went to bed just after 3am. It is a lot to take down and pack, but manageable. Must remember finderscope next time! Dew heaters, better eyepieces, coma corrector, barlow & binoviewers, etc are all on the shopping list, but it will take some time to replenish the piggy bank. Not in a rush, summer is almost here! Hoping for a bit more viewing before the nights are too short. Cheers all for your help along the way.

[Ships and Stars]

Wanted to quickly add I wasn't 100% sure this scope would work ok, so just being able to scan the sky in focus was a massive relief. It was purchased sight unseen, second hand (though never used) and apparently not covered under warranty as far as I know. That's why I was particularly nervous (and equally relieved) to quickly test it out. Once I've built up some time with the Stargate later this year, I'll write a more experienced review, though still far from expert, mind! Thanks all. 

[John]

Glad it's working out well for you - bit of a step up from a Tasco 60mm

It's a scope with a lifetimes observing potential so you should have years of satisfaction from it once you have mastered it's "little ways".

You can't actually damage your eye by observing the moon without a filter with the scope but it will seem extremely bright so I'm not surprised that filtration is needed to make the view more comfortable.

I wish I lived closer to you - I could bring along my 100 degree Ethos eyepieces and an O-III filter and blow our minds with with the views of globular clusters, the brighter galaxies, planetary nebulae and the wonderful Veil Nebula

I've observed some of these targets with a 20 inch scope under dark skies so have some idea on what you have in store - you lucky person !  

[Ships and Stars]

1 hour ago, John said:

Glad it's working out well for you - bit of a step up from a Tasco 60mm

It's a scope with a lifetimes observing potential so you should have years of satisfaction from it once you have mastered it's "little ways".

You can't actually damage your eye by observing the moon without a filter with the scope but it will seem extremely bright so I'm not surprised that filtration is needed to make the view more comfortable.

I wish I lived closer to you - I could bring along my 100 degree Ethos eyepieces and an O-III filter and blow our minds with with the views of globular clusters, the brighter galaxies, planetary nebulae and the wonderful Veil Nebula

I've observed some of these targets with a 20 inch scope under dark skies so have some idea on what you have in store - you lucky person !  

Hi John, yes hoping I get many years use out of it and hoping others can have a look as well, especially if they bring nice eyepieces! ? So far it's been fairly simple to assemble and use, and after a few more sessions it should go smoothly. Dew heaters are a must as I've quickly learned, otherwise the night can be cut short in a hurry. The moon was extremely intense through the mirrors - wasn't sure if it could cause permanent damage, but it was borderline painful! Amazing though. My main desire it to observe DSOs, which is why I was lusting after this one. The Veil nebula is on my list if I get another go before summer. I think for a lot less ££, the 18" non-GOTO looks appealing as well. Should you find yourself wandering around NE Scotland with a selection of Ethos eyepieces, do call in! Cheers John!

[callisto]

Nice report.......Ahh, them 60mm red Tasco days, first ever view of Jupiter and moons........Great

 

Mark.