iOptron HEM27 Initial Review and Info

[Ed217]

Had the HEM27 out for the second time last night and was fairly clear for a few hours. Generally things seemed to work well other than PHD2 (see below). Moon was out for all of the time, so that limited what could be captured somewhat.

For reference I only do imaging for astro things and rarely ever do visual things. I set up outside with the mount, scope and a small miniPC for processing. I use an Intel NUC at the scope for this. I have a small LCD display I can use there for setup and PA steps. I did this last night and did the initial GOTO steps and testing there.

I later moved inside where I have a second miniPC that connects to the scope unit via a Wifi setup. That works really well for me as all imaging is still done and stored at scope but viewable inside. I have a similar set I use for my car when I do imaging at remote sites. That way, it’s cool in the summer and warm in the winter. I only took a few images last night as I was more interested in seeing what worked well and what didn't.

I only did a few actual images last night as I wanted to focus on basic operations. One of these is referenced below for Vega and the region near it. This was a quick exposure at gain 125 and a 30 second exposure.

https://www.astrobin.com/kmc01h/

Longer exposures later ran into trouble with PHD2 which is discussed later.

I did a polar alignment first using the iPolar scope that is integrated into the HEM27 model I got. That worked really well and was easy to use. I have an existing iPolar unit I already used with a Celestron AVX scope, so am used to this part. Got it alignmed and it stayed that way pretty much the entire time. I did the initial PA with only the mount on the iOptron carbon fiber tripod. I later updated that when I added the WO GT71 scope and ASI294MC Pro camera, EAF focuser and cabling.

I then did a GOTO alignment to update the PA for actually finding objects. I did the initial run for this using the Moon. It quickly slewed to the area for the Moon and it was visible in the lower left part of the frame. I then used the “Sync to Target” option to update the position. I used the arrow keys on the HC to center the moon in the center and then the “Sync to Target” choice. From that point forward it was able to GOTO directly to any selected object. I selected a couple of different stars over the few hours and it went to each quickly and had the star dead center in the view. This part worked amazingly well. Slewing is also very fast when the MAX slew rate is set and used. As a comparison, my AVX mount is much slower.

It also has a “goto to zero position” choice which quickly returned the mount and scope to the home position. I did this a few times over the night to check the balance of the scope and adjust as necessary. When you slew back to the same star, it goes there quickly and dead center.

The HEM27 has two latitude ranges for use (15-41 and 39-65). To change from one to the other is an involved process involving many small parts. I would never want to try this at an actual imaging site when it was dark. Even doing it inside takes time and care. You have to remove a number of bolts and screws. If you don't get it put back together correctly you will likely limit your latitude range at one end or the other. This happened to me the first night I had the unit out. The section involving the latitude knob and two brass screws is tricky. The same is true for the position bolt and two small black tube sections. Getting these lined up after removal can be difficult as there is little extra room or play.

All tightening is done using an allen wrench that is stored in the mount itself. This will be used many times in doing a PA with the scope and mount. There are at least 6 different parts to be loosened and tightened.

The mount has a bubble level, but its placement makes it difficult to see. You can't look down on it as the mount head structure blocks this view. Your only choice is to view from the side and that is less than accurate. On my AVX mount I have a DIY created level I use that works much better. It’s much larger and has two levels that are very easy to see from the side and very sensitive to movement. The one I use is like this one:

https://www.lowes.com/pd/Swanson-Tool-C ... el/3585802

I have a 3D printed part that is attaches to which makes it have the right angle when added to the button of the AVX mount. A friend from a rocket club printed this for me. You can find the specs on ThingAVerse. This is an image of how this looks:

https://www.cloudynights.com/gallery/im ... img-0606b/

I am going to get another one of these and see if it can just be added to the bottom area of the HEM27 for similar use. Figure 11 in the HEM27 users manual shows this area. I think it will fit on the back side of the base plate.

A big plus for me for the HEM27 is the lighter weight. As the years tick by, moving heavy stuff is hard on my back. It’s hard to avoid back pain after using the AVX with setup and tear down. The AVX mount (before counter weight) and tripod is 35 lb. The HEM27 is 13 lb for both. I also store the HEM27 with the mount attached to the tripod, which results in fewer steps for setup and tear down. The HEM27 also has no counterweight for normal loads, so less weight and steps there as well.

This is the imaging train from last night (no cables or miniPC). The second is what I intend to use for level using the same device I used on the AVX.

https://www.cloudynights.com/gallery/im ... -img-0863/

https://www.cloudynights.com/gallery/im ... -img-0865/

[prusling]

Thanks for posting this Ed. Very interested to hear more - especially guiding experiences.

[Greenman]

Sounds promising Ed, enjoy the new kit.

[Ed217]

Thanks for posting this Ed. Very interested to hear more - especially guiding experiences.

I have had the mount out a couple of nights so far, one of which has reasonable clear skies for an hour or two. This is a bortle 6 area in the city, but reasonably dark around the scope. The basics for that night were:

HEM27 mount w/iPolar
iOptron carbon fiber tripod
William Optics GT71 scope
Simple 2 way level from Lowes
ZWO ASI294MC Pro camera
ZWO EAF focuser
ZWO 30mm guide scope
ZWO 120mm-S guide camera

The guiding results looked like this:

The typical guideline for imaging and guiding is that your guiding RMS is half or less than your imaging rig image scale. For the combo listed, image scale is 2.84 and overall guiding RMS is 1.07. That’s clearly in range and the resulting image shows nice round stars and no trails or movement artifacts. A few of my other imaging runs had RMS in the 0.2 to 0.5 range. Time will tell what the typical average yields.

One image that resulted from that session is shown here:

https://www.astrobin.com/avcx10/

Ed