Explore Scientific, 16 inch / F 4.5 Truss tube Dobsonian

Explore Scientific, 16 inch / F 4.5 Truss tube Dobsonian

Hello all. I’m a brand new member of Cloudy nights. Been here a few times as a guest.

 I’m from the city of Pune, in Western India. I’m not a complete novice when it comes to stars and constellations as I’m a mariner by profession but DSOs have been a fascination for a long time. I intend to be a visual astronomer for the near future before I dabble in any AP other than the Moon.

This is my first post about the brand new scope that I bought a few days ago. The decision to buy this particular one stemmed from having seen a 12 inch GSO collapsible tube Dob at a Star party a few months ago. Orion looked pretty sweet through that 12 incher hence logic demanded that it would look sweeter still through a 16 incher.

Hope this experience of mine helps someone to make a decision.

This one took its own sweet time coming home. I paid 100% advance to the dealer in February of this year with the condition that it will be delivered by the 1^st week of March. Port congestions in China and Singapore delayed the ship carrying my precious cargo. You can imagine my chagrin, when I had been tracking the ship across the oceans using ‘Findship app’ on my phone (and teaching the dealer to do the same….lol). Anyways, the scope got home by the 9^th of April a good 6 weeks later.

It came neatly packed in double lined cardboard boxes. Assembly was a breeze since all I had been doing the weeks prior was watching YouTube videos about assembly and collimation. Took me about 20 mins or so to get the thing fixed. Boy is it huge and boy, is it heavy!!!!

All things considered, that’s the only blunder I think I’ve made. I have grossly underestimated the size and weight of this thing!! But no matter…….I decided to soldier on.

As with all star gazers on all planets across all galaxies across Multiverses, Murphy decided that since I got a brand new scope, it ought to rain every day for the next 8 days!! It is practically unthinkable to have rains in my part of the world in April as it’s the peak of Summer with temperatures hitting the low 40s (I mean Celsius and not Fahrenheit). 40⁰ C is a 104⁰ to my American brethren.

On the 9^th day, with clear skies, a light heart and a bent back, I assembled the scope in my garden and had my first light!!!!

AND IT WAS AAMAZINGGGLYY…………underwhelming……Wait….whaatttt??!!

That’s the moment when the true meaning of a Bortle 7 sky hit me like a ton of bricks...

I mean, I could see stuff that would have been visible through a 50 dollar binocular. I could make out binary stars, a whiff of the Orion Nebula, Pleiades but I had built up such massive expectations about seeing DSOs that I was sorely, bitterly, utterly disappointed..(You may add any other adjectives that come to mind)

I was a confused man wondering if I made a mistake buying this scope, wondering if the scope was collimated, wondering why stars looked like comets upon magnification, wondering why I couldn’t see jack, wondering if I was using the wrong eyepiece, wondering why there was a blurred black circle in the centre of my optical path, wondering if my assembly was correct. So many questions and no answers.

 A few posts on Facebook groups gave me some solace and advice regarding viewing conditions, dark sky requirements and expectations versus reality. Needless to say that it was a bitter pill to swallow.

Someone there suggested Cloudy nights as the fountain of knowledge. So ended up here as a guest.

Got myself a laser collimator...

Only to learn that I had to collimate the collimator before I could use it to collimate the scope. For a brief fleeting moment I could hear Juvenal whispering “Quis custodiet ipsos custodes?”In my ears.

Been there- done that now.

Learnt about focusser extension pieces that need to be screwed on to the focusser tube to get to focus.

The next few days ended up with me doing quite a bit of reading and getting opinions from good people like you all on this forum and many more. I decided to improve the things that I could.

Below are the few things I improved upon:

1.       Manual Setting circle

Operating a fast scope as this without a reference is like looking for a needle in a hay stack. You need to have a fairly accurate pointing accuracy if you are to find anything at all in the sky that isn’t immediately obvious.

So I downloaded a setting circle from blocklayer.com (Eternally grateful to John Dreese of Reflactor on

You tube for giving me the idea). Link to the video here in case anyone is interested. https://www.youtube.com/watch?v=bUEhm2fB13M

 Got that printed and pasted it on a 2mm board, which I then cut in to a 28 inch circle. Fitted that under the rocker box. Used my digital clinometer that I use for wood working to give me the altitude angle. This setup gave me a bearing to point the scope and an altitude angle to aim the scope up.

Viola!!! I was in business.

I got the Stellarium app on the phone. Aligned my scope to Venus, read the azimuth and altitude off Stellarium and adjusted the setting circle accordingly and fixed it to a ground reference. After that I could point the scope to any object of interest just by using the setting circle and clinometer by getting the azimuth and altitude of the object from Stellarium.

2.       Shroud

The dealer couldn’t supply the shroud along with the scope as no stocks available. So got one made from a local tailor. It’s not great as the fabric isn’t elastic but it gets the job done. I need to get the fabric out of the optical path at times. Will get a proper one soon. A shroud greatly improves the contrast on this design.

3.       Closing the open ring around the secondary mirror to improve contrast

Steam bent some wood veneer lying at home and bent it around the secondary mirror frame. Painted it matt black on the inside and some PU polish on the outside. Anything to increase contrast I suppose.

4.       Laser pointer instead of red dot finder

The Red dot finder supplied with the unit wasn’t really impressive so I replaced it with a green laser pointer in a bracket. There don’t seem to be any legal issues with using a laser pointer in my part of the world. So this works very well once it is aligned with the scope. Makes bending and looking through red dot finders or finder scopes unnecessary.

5.       Adjustable stool for observation

The constant bending for observation at low altitudes was taking a toll on my back. Lots of adjustable stools in the market but none available in India. A hearty thanks to the good people on FB fora who guided me to the DIY by Mark Parrish on Cloudy Nights. A hearty thanks to Mr. Parrish for giving me the idea. Made a quick and dirty version of the stool with scraps lying about in my workshop, some aluminium extrusions, and nuts n bolts. This more than serves my purpose. I can observe seated comfortably now.

I was a bit apprehensive of whether this beast would fit in my hatchback if I were to go to a dark sky site. It did!! The mirror box comfortably stowed in the boot, with the secondary mirror ring beside it. The rocker box in the back seat and off we went to a dark site a 100 Kms away from home. We managed to get to a Bortle 4 sky.

Now here comes the funny part. I did not bother to check the lunar ephemeris before leaving home.

I drove a 100 Kms to a Bortle 4 sky only to be greeted by a bright Gibbous moon overhead at the start of the evening!!!

I went red in the face and the wife had a good laugh.

Hmm, I did what I normally do….I soldiered on…

Took me 10 mins this time to set up the scope. Another 5 mins to collimate the whole rig, align my Home-made setting circle with the sun to zero in my rocker box and wait for the Sun to go down and enjoy my actual first light, in a manner of speaking.

And Ladies and Gentlemen, what an awe inspiring sight it was!!!

The Sun was behind the hill out of my sight but very much above the horizon and I could already see double stars!! With the Sun below the horizon, I aimed at the Orion using my Explore scientific 40mm/52⁰ eyepiece. It was an amazing sight. With the sky still relatively bright, I could make out Blue, green hues of the Nebula. The green could be a matter of debate, since I could see the blues and my Son claimed to see some green as well.

By the time it gets dark, Orion gets quite low over the western horizon this time of year. So we enjoyed it a bit before moving on to Venus. Clear darkish skies and a stable atmosphere made all the difference in the world. I could easily zoom progressively in to Venus up to the point where the phase could be easily made out without blurring. Couldn’t say the same about Mars. Probably too far for a decent view.

Next on the agenda was a star cluster. Stellarium performed beautifully as it gave me directions for M3.

To be honest, up to this point I was really not confident about my home-made setting circle and digital clinometer as I had only tried it at home in a light polluted sky and could not see any DSOs there.

But this time around, I just turned the scope to the correct bearing, rocked the scope to the correct altitude and looked through the eyepiece. There in the centre, was M3, in all its glory, in spite of that bright Gibbous Moon!! What a sight it was. My son and I high fived each other, clapping our backs, congratulating each other for making a setting circle that works!!!

I do realize that there’s no rocket science to it but the thrill of making something and to see it work as intended….

Ah, the joys of the little pleasures in life… The stuff that memories are made of.

After that it was Globular cluster season the entire night.

I will stop my ranting here people. I’m really glad I bought this scope. I love the quality of the optics.

Learning to collimate well has made a phenomenal difference to what I see now.

The Moon is beyond words through this scope. So are the stars and nebulae. Venus was beautiful.

 A brief glimpse of M81 before clouds spoilt the show was such an amazing moment. To have seen a galaxy with my own eyes even if it looked like a blurry smudge of light!!! A GALAXY!! An entire Galaxy through a 2 inch hole in a man-made contraption... The more I ponder, the crazier it seems. Can’t wait for Andromeda season.

Yes, it is huge and yes it is heavy but it is exactly as advertised. It is absolutely portable. I could dismantle and stow the whole rig, the wife and 1 and a half kids into my hatchback and drive a 100 Kms without too much discomfort. The next time would be a Bortle class 2 sky some 190 Kms away. I suppose we will take breaks more often along the way to stretch our legs. The mirror box is heavy but nothing that an able backed person couldn’t handle. Anyone interested in this one has my whole hearted endorsement.

Clear Skies and God bless.