Explore Scientific 152mm Maksutov-Newtonian Comet Hunter

[Moon Watcher]

This summer I organized a star gazing event at a location with virtually no light pollution on an island in Lake Michigan where 25-30 people turned up.  The sky was just incredible with the Milky Way brightly painted across the summer sky.

One of the scopes I used was the Explore Scientific 152mm Maksutov-Newtonian Comet Hunter.  

The scope pulled up objects like M57 and M13 so clearly and with such detail that people were lingering at the eyepiece commenting on how beautiful they were.  I didn’t have to explain how that tiny fuzz ball was a star cluster, it was obvious that M13 was a ball of stars; this says a lot about the resolution and optics.  Similarly, the double-double Epsilon Lyrae was obvious to laypeople with a TeleVue 20mm Type 5 and 2x Powermate.  The colours of Albireo also got ‘oohs’ and ‘aahs’. 

When M31 rose, the scope, paired with an ES 30mm 82 degree AFOV (no slouch either!) with it’s wide flat field displayed the entire galaxy with its’ satellites and may be one of the best views I have ever had of Andromeda.  Even at just 6 inches of aperture, the Veil Nebula under the pitch black skies was just lovely and people had fun placing the lumicon OIII filter back and forth in front of the 30mm eyepiece. They found the Veil blinking in and out of view fun.  One young person called it magic!

The highlight though, was a walk through the Sagittarius region of the Milky Way.  I let people use the controller on the Celestron AVX mount to cruise around and they would ‘oooh’ and ‘aaagh’ for minutes at a time.  The view of the Lagoon and the Trifid in the same field was just jaw dropping. Using a Lumicon OIII filter actually made them ‘glow’ from the inside.

At higher power (TeleVue 5mm Type 6 82 degree AFOV), we had excellent detailed views of M51 where the arms were actually visible.

 

The only negative is the collimation process.  The 3 adjustment knobs should make the process easy and tool free.  However, as someone who owns both Newtonians and SCTs that I routinely collimate, this scope was a bear.  The reason is that the central bolt (that in other scopes adjusts the height of the secondary up and down the tube) isn’t actually screwed into the secondary housing; it merely abuts against the secondary to push against the 3 adjustment screws.  In effect, the 3 adjusters are used to raise, lower and tilt the secondary and the central bolt then tightens down against the secondary to lock it in place.  Once that was figured out, collimation was easy and rarely needed adjusting.

 

In summary, the Explore Scientific 152mm Maksutov-Newtonian carbon fibre scope is great.  Explore Scientific service is excellent; they immediately shipped a new focuser when I told them the original appeared to be damaged upon arrival.  The fast (f4.8) scope with the ES 30mm eyepiece yields an absolutely flat 3.4 degree FOV with tack sharp stars to the edge and the wide field regimen is where it excels. High power views of planets and galaxies are at least as good as my 130mm f7 triplet apochromat.  The scope is well constructed with a smooth heavy duty 2" focuser and the carbon fibre tube looks very handsome mounted to the AVX mount in the living room.  I would highly recommend this scope to beginners and advanced amateurs alike.

 

[Chris]

Very nice review  I sometimes look at this scope whilst window shopping, and to hear that it's at least as good as a 130 triplet makes me want to own one someday  

[John]

Interesting report

I used to own an Intes MN61 6" F/5.9 maksutov-newtonian and it was a superb scope - very refractor-like images. I ran it side by side with my ED120 refractor for quite a while and the two were virtually identical in performance on the moon and planets with the mak-newt having the edge on deep sky objects because of it's larger aperture of course.

You don't see many reports on the ES mak-newts so it's good to read one

[Moon Watcher]

Hey Chris and John,

The ES Mak-Newt is pretty amazing - especially for the price.  I compared it directly with my Teleskop-Systems Photoline 130mm f7 triplet which by itself is a beautiful scope.  The triplet gives crystal sharp views with no false colour after equilibration and its views of Jupiter with ever finer and finer bands and festoons is just something to behold.  However I have to say that the ES scope beats it in terms of details on planets and on deep sky objects, as you found in your comparison with the SW 120ED.  I also got my neighbours to look through both to get an unbiased comparison and they all agreed that the ES won.

When compared to the 11" SCT, the SCT shows such beautiful detail on solar system and deep sky objects that time stops while looking through the eyepiece.  But the curved, restricted field of view fails the SCT on extended objects like the Veil, double cluster, M31, or coasting along the Milky Way.  That's where the Mak-Newt really shines.  The wide, flat, crisp view is the single reason I bought it and why it's going to remain part of my scope collection.

 Growing up with crappy Dixon store binoculars in... Luton of all places... I never thought that  in years to come I would be looking through a carbon fibre 6" Maksutov-Newtonian scope for a few hundred dollars.

Cheers all

Avtar

Ps attached a photo of the ES on my old Super Polaris Celestron mount (circa 1984-85, purchased with a 6" newtonian from Astro Systems Luton Beds for 600 pounds).  The 2 work great together for ambling around the sky. 

 

[John]

I found my Intes mak-newt equalled the ED120 on planetary detail but didn't beat it. The extra aperture did show deep sky objects a bit better as you would expect.

I decided to keep the ED120 because it cooled down quite a bit faster than the mak-newt and it was quite a bit lighter making it easier to mount.

Ed Ting used to list the Intes MN61 Mak-Newt as one of his favourite all-time scopes, which is quite a compliment !

I'm glad you are enjoying your ES refractor and mak-newtonian - the are clearly both fine scopes

Funnily enough my 1st proper scope was one of the Astro Systems 6" newtonian as well !

 

 

[laudropb]

Very nice report and review.

[JonathanA]

On 15/10/2016 at 18:33, Moon Watcher said:

 

The only negative is the collimation process.  The 3 adjustment knobs should make the process easy and tool free.  However, as someone who owns both Newtonians and SCTs that I routinely collimate, this scope was a bear.  The reason is that the central bolt (that in other scopes adjusts the height of the secondary up and down the tube) isn’t actually screwed into the secondary housing; it merely abuts against the secondary to push against the 3 adjustment screws.  In effect, the 3 adjusters are used to raise, lower and tilt the secondary and the central bolt then tightens down against the secondary to lock it in place.  Once that was figured out, collimation was easy and rarely needed adjusting.

Hi,

Recently bought the comethunter.  I was really interested in your coment about collimation. I've spent hours on getting it right - secondary was well out on receiving it. It is still slightly too far down the tube towards the primary so even though I have the primary centred with the secondary and the secondary with the focuser tube, one edge of the mirror is very slightly clipped on viewing with a collimation cap or Cheshire (when I rack out the focuser).

I've worked out the 3 thumb screws and have loosened the centre bolt which gave me extra degrees of freedom with the thumbscrews before re-tightening, but, despite a lot of fiddling,  I can't work out how to shift the secondary just a touch further away from the primary. When the centre bolt is rotated it doesn't seem to shift the secondary by itself but just seems to free up the thumbscrew adjustment. It looks like you might know how to do what I want....though maybe I'm worrying about nothing. I've had limted clear skies since purchasing just enough for a quick view of the moon between the clouds and no problems seemed evident in the view. I will mostly be imaging with it though so would like to get it right.

One other issue is that it seems to be impossible to get the outline of the secondary to be completely circular. This has been easy with Newtonians I've owned. Is this because of the outsize mirror and it being a Mak Newtonian? I'm not worrying to much as I can get a perfectly circular image of the primary with clips which I guess is what really matters.

BTW - the instructions for collimation in the manual are rubbish: the seem to be written for a Newtonian and the adjustment screws and bolts are completely different. It would be good if ES could update this.

[Adam J]

Have wanted one of these for ages. Can I ask, do you know if I could fit a DSLR and 2" filter draw / wheal into the back focus?

[JonathanA]

Hi Adam J.  Not completely sure but with DSLR and a standard adaptor I was getting a nasty diffraction spike on bright stars. It may have been the particular  comethunter I first received that was the problem but with help we traced it to the focuser draw tube protruding too much into the light path. I am now on a second comethunter and the problem has disappeared but that maybe because I have now got a very low profile adaptor. I haven't been able to test the original configuration as have mostly been clouded out. It maybe that the filter wheel would mean that you had too much drawtube in the light path. I'll repost when I have been able to do more testing. In the meantime the views I have had through the scope have been fantastic - really contrasty, best ever views of M31 and associated galaxies.

[Moon Watcher]

On 12/18/2016 at 08:47, JonathanA said:

Hi,

Recently bought the comethunter.  I was really interested in your coment about collimation. I've spent hours on getting it right - secondary was well out on receiving it. It is still slightly too far down the tube towards the primary so even though I have the primary centred with the secondary and the secondary with the focuser tube, one edge of the mirror is very slightly clipped on viewing with a collimation cap or Cheshire (when I rack out the focuser).

I've worked out the 3 thumb screws and have loosened the centre bolt which gave me extra degrees of freedom with the thumbscrews before re-tightening, but, despite a lot of fiddling,  I can't work out how to shift the secondary just a touch further away from the primary. When the centre bolt is rotated it doesn't seem to shift the secondary by itself but just seems to free up the thumbscrew adjustment. It looks like you might know how to do what I want....though maybe I'm worrying about nothing. I've had limted clear skies since purchasing just enough for a quick view of the moon between the clouds and no problems seemed evident in the view. I will mostly be imaging with it though so would like to get it right.

One other issue is that it seems to be impossible to get the outline of the secondary to be completely circular. This has been easy with Newtonians I've owned. Is this because of the outsize mirror and it being a Mak Newtonian? I'm not worrying to much as I can get a perfectly circular image of the primary with clips which I guess is what really matters.

BTW - the instructions for collimation in the manual are rubbish: the seem to be written for a Newtonian and the adjustment screws and bolts are completely different. It would be good if ES could update this.

Hey Jonathan,

To move the secondary away from the primary, loosen the center bolt and then turn the 3 thumb screws clockwise.  This should pull the secondary up the tube.  Once you have it centered in the cheshire or collimation cap, tighten the main bolt down.  The issue is that when the center bolt touches the secondary housing as you tighten, it slightly rotates the secondary clockwise.   Then you have to rotate the entire secondary housing to re-center by loosening the assembly on the corrector plate.  It sounds scarier than it is.  I ended up disassembling the entire corrector plate and secondary just to figure out how to collimate.  However, once it was clear that the center bolt doesn't move the secondary but just locks it in place after adjusting with the 3 thumb screws, it became obvious how to go about collimating the thing.

And I agree that ES could do a lot better with their instruction manual!  

Good luck!

 

[niallk]

Great review! Sounds like a top performer 

I know what you mean about the secondary - I had to loosen the one on my SW to understand a similar mechanism, and have the right mental picture of what's going on when making adjustments.

[JonathanA]

20 hours ago, Moon Watcher said:

Hey Jonathan,

To move the secondary away from the primary, loosen the center bolt and then turn the 3 thumb screws clockwise.  This should pull the secondary up the tube.  Once you have it centered in the cheshire or collimation cap, tighten the main bolt down.  The issue is that when the center bolt touches the secondary housing as you tighten, it slightly rotates the secondary clockwise.   Then you have to rotate the entire secondary housing to re-center by loosening the assembly on the corrector plate.  It sounds scarier than it is.  I ended up disassembling the entire corrector plate and secondary just to figure out how to collimate.  However, once it was clear that the center bolt doesn't move the secondary but just locks it in place after adjusting with the 3 thumb screws, it became obvious how to go about collimating the thing.

And I agree that ES could do a lot better with their instruction manual!  

Good luck!

 

Thank you Moonwatcher. That's just what I needed to know. I know what you mean about the secondary housing - mine hadn't been tightened down so it rotated every time I took the cover off the thumbscrew unit.  Thanks again.

[JonathanA]

On 19/12/2016 at 20:46, Moon Watcher said:

Hey Jonathan,

To move the secondary away from the primary, loosen the center bolt and then turn the 3 thumb screws clockwise.  This should pull the secondary up the tube.  Once you have it centered in the cheshire or collimation cap, tighten the main bolt down.  The issue is that when the center bolt touches the secondary housing as you tighten, it slightly rotates the secondary clockwise.   Then you have to rotate the entire secondary housing to re-center by loosening the assembly on the corrector plate.  It sounds scarier than it is.  I ended up disassembling the entire corrector plate and secondary just to figure out how to collimate.  However, once it was clear that the center bolt doesn't move the secondary but just locks it in place after adjusting with the 3 thumb screws, it became obvious how to go about collimating the thing.

And I agree that ES could do a lot better with their instruction manual!  

Good luck!

 

Guess what? I followed Moon Watcher's advice and great collimation achieved. It worked just as described (and even better, without the need for compensatory adjustment at the end).  The above would be a useful paragraph to have in the manual.  Thanks again.

[Moon Watcher]

Hey Jonathan,

thats great!   Once collimated the scope is pretty amazing.  You'll enjoy the views!

cheers

Avtar aka Moonwatcher