Skywatcher 250px dobsonian first light

[Victor Boesen]

Since I got interested in astronomy, my dream telescope has always been a ten inch dob. A few days ago I got the skywatcher 250px dob which I bought together with three explore scientific 82 degree eyepieces.

Two days ago I had my first light, but collimation was a tad off. I collimated it the day after, and had even clearer skies.

Observing:

First of all, I could see more colours in the stars than I could with my old 6 inch reflector. After collimating the scope I could also see spikes on the bright stars, but precise spikes.

I began with star hopping to m81 and m82. For this I used my 24mm 2" eyepiece. This eyepiece is very nice for star hopping. When star hopping, you can clearly identify these galaxies when you see them. Even tho the sky wasn't totally dark I could still see m82 as a long pencil while m81 was more of a blob. when it became darker m81 was more like an elongated disk.

The next target was jupiter since it had just swung into view from my balcony. On stellarium it said that Io would cast its shadow onto the disk, so I wanted to try and see if I could see the shadow. I observed with the 14mm explore scientific at 85x and the cloud bands stood out bright and with loads of contrast. I tried with my 4,7mm but I found that it was a bit too much magnification (255x). I then tried the 14mm with my 2,5x barlow which gave me 214x and this worked out better, but not as good as with the 14mm only. I think the sweet spot for me would be with an 8,8mm eyepiece (added to wishlist). 
At one point observing jupiter, the jetstream was very calm so I had a crisp jupiter with a shadow as clear as a black dot on a piece of white paper through the hole field of view.

 

Conclusion:

I found it very easy to nudge the scope from a to b, and when I was on target, the view was crisp and clear even from inner city where I live.
I have never seen jupiter this clear, not even from a rural area with the milky way visible.

Clear skies
Victor Boesen

[laudropb]

Very nice report Victor. It's good to see you are having success with your new scope.

[Pondus]

Nice report Victor.

And I agree With adding the 8,8mm to Your eyepiece set.

 

Rune

[Victor Boesen]

3 minutes ago, Pondus said:

Nice report Victor.

And I agree With adding the 8,8mm to Your eyepiece set.

 

Rune

Thanks! I will be adding the first light to my website (I remember you from my other topic:-)

[Pondus]

Just remember, even in lovely Southern Denmark planets will be very low for the Next few years.

For me, living at 59N its quite hopeless regarding planets.

I`m waiting for Mars to appear high in the sky, late 2020 .

PS Hows Your site going?

[Victor Boesen]

1 minute ago, Pondus said:

Just remember, even in lovely Southern Denmark planets will be very low for the Next few years.

For me, living at 59N its quite hopeless regarding planets.

I`m waiting for Mars to appear high in the sky, late 2020 .

PS Hows Your site going?

The only planet thats high in the sky is jupiter. The other planets are very low (20 degrees).

I have not posted more on my site but I will be posting a first light, and a review of the scope and eyepieces.

[Charic]

Plössl's have an apparent field of view somewhere around the 50° mark (mine are supposedly 52°) but field aside, how does your 10mm eyepiece fare regarding the 'sweet spot'. I would be inclined to go somewhere that is twice the telescopes focal ratio! You have two, depending on how you do the sums? You'll either calculate using a 250mm or 254mm mirror. I have a 200/203mm giving f/5.9 and  f/6 , requiring a 9.6mm EP. The 12mm works best. On your scope you have f/4.8 or f/4.7 (or f/4.75 to be in the middle) now an eyepiece of twice the focal ratio would require a 9.5mm, the reason I suggest a 10mm would be closer to the sweet spot. A 10mm can also be Barlowed well giving you 240x well within the practical limits of your scope.

That's the theory I adopt and it seems to work in most cases, and  even reverse engineering some of the eyepieces that are favoured by some folk, that  they feel are the best for their needs has resulted in the fact that they are multiples of or closely related to that all important focal ratio!
 Even though its often said the focal ratio is not of any importance for users that partake in visual use only, its a good marker for buying eyepieces.

One advantage you have over my scope is the aperture, it has headroom for more detail, even if we used and swapped the same eyepieces, viewing from the same site, your scope should produce more detail. Not only that, you have already seen for yourself, the detail increases as you user longer focal length eyepieces, and diminish as you ramp the power up. Its finding that middle ground thats suits you most, the eyepiece needs to be comfortable with sufficient eye-relief and sufficient field of view to satisfy you needs. Finding that eyepiece can take some time. It was my wish to have purchased a 12" Skyliner solid tube, even bought the Delos EPs to account for the low focal ratios (another consideration to ponder when choosing eyepieces for your scope ?

But whatever your doing, it seems to be working well for you at the moment, which can't be said for the rest of us here in the uk, at present!
 

[Astro Imp]

Nice report Victor. It's always good to hear enthusiastic first light reports. 

Keep enjoying your scope and hope you have plenty of clear skies.

[Victor Boesen]

4 minutes ago, Charic said:

Plössl's have an apparent field of view somewhere around the 50° mark (mine are supposedly 52°) but field aside, how does your 10mm eyepiece fare regarding the 'sweet spot'. I would be inclined to go somewhere that is twice the telescopes focal ratio! You have two, depending on how you do the sums? You'll either calculate using a 250mm or 254mm mirror. I have a 200/203mm giving f/5.9 and  f/6 , requiring a 9.6mm EP. The 12mm works best. On your scope you have f/4.8 or f/4.7 (or f/4.75 to be in the middle) now an eyepiece of twice the focal ratio would require a 9.5mm, the reason I suggest a 10mm would be closer to the sweet spot. A 10mm can also be Barlowed well giving you 240x well within the practical limits of your scope.

I have never thought of this. I will give it a try next time.