It’s always exciting to try out a new setup for the first time, although the net result is generally a picture of all the work that needs to be done as much as pictures of celestial objects.
This first test image is of M94, a face on spiral galaxy in Canes Venetici (the Hunting Dogs) comprised of 40 stacked 30s images in Luminence. Despite the pretty short exposure the centre of the galaxy is pretty blown out so capturing details of the bright inside structures along with the dimmer ring structures will take some creative exposures. I’m looking forward to exploring how to make this image better! This image taken with a ZWO ASI183MC monochrome camera and a ZWO filter wheel on a 10″ F/4.7 Newtonian reflector.
One thing I learned is stray light can be seen in the images! I normally have a red light pointed at the telescope so I can see what it’s doing but in this telescope it’s clear that any stray light can make it’s way into the sensor (in this case apparently through the open back of the telescope) so I’ll have to keep the lights out.
First tracking needs to be improved on the NEQ6 mount to allow exposures longer than 30s (when attempting 60s sub-exposures there was star trailing so clearly there are issues.) Likely balance is the culprit – the telescope is quite heavy and may be exceeding the mount’s ability to track accurately while carrying all that weight but I’ll try careful balancing and see if that helps.
I was able to get the mount very accurately polar aligned with my Orion P1 Polar Alignment Camera so I know the issues with tracking are inherent in the mount rather than a result of imperfect polar alignment.
My autoguiding system needs to be set up as well. This consists of the small 50mm telescope with an Orion Starshoot Autoguider camera attached to it. When guiding is running the EKOS software I use locks onto a star and makes small adjustments to the position of the telescope when the star appears to drift. However no amount of guiding will help if the mount is really out of whack. Lots to do before the summer solstice!
M94 is classified as having a low ionization nuclear emission region (LINER) nucleus. LINERs in general are characterized by optical spectra that reveal that ionized gas is present but the gas is only weakly ionized (i.e. the atoms are missing relatively few electrons).
M94 has an inner ring with a diameter of 70 arcseconds (″) (given its distance, about 5,400 light-years (1,700 pc)) and an outer ring with a diameter of 600″ (about 45,000 light-years (14,000 pc)). These rings appear to form at resonance points in the disk of the galaxy. The inner ring is the site of strong star formation activity and is sometimes referred to as a starburst ring. This star formation is fueled by gas driven dynamically into the ring by the inner oval-shaped bar-like structure.
A 2009 study conducted by an international team of astrophysicists revealed that the outer ring of M94 is not a closed stellar ring, as historically attributed in the literature, but a complex structure of spiral arms when viewed in mid-IR and UV. The study found that the outer disk of this galaxy is active. It contains approximately 23% of the galaxy’s total stellar mass and contributes about 10% of the galaxy’s new stars. In fact, the star formation rate of the outer disk is approximately two times greater than the inner disk because it is more efficient per unit of stellar mass.
There are several possible external events that could have led to the origin of M94’s outer disk including the accretion of a satellite galaxy or the gravitational interaction with a nearby star system. However, further research found problems with each of these scenarios. Therefore, the report concludes that the inner disk of M94 is an oval distortion which led to the creation of this galaxy’s peripheral disk.
In a paper published in 2004, John Kormendy and Robert Kennicutt argued that M94 contains a prototypical pseudobulge. A classical spiral galaxy consists of a disk of gas and young stars that intersects a large sphere (or bulge) of older stars. In contrast, a galaxy with a pseudobulge does not have a large bulge of old stars but instead contain a bright central structure with intense star formation that looks like a bulge when the galaxy is viewed face-on. In the case of M94, this pseudobulge takes the form of a ring around a central oval-shaped region.
In 2008 a study was published showing that M94 had very little or no dark matter present. The study analyzed the rotation curves of the galaxy’s stars and the density of hydrogen gas and found that ordinary luminous matter appeared to account for all of the galaxy’s mass. This result was unusual and somewhat controversial, as current models do not indicate how a galaxy could form without a dark matter halo or how a galaxy could lose its dark matter. Other explanations for galactic rotation curves, such as MOND, also have difficulty explaining this galaxy. This result has yet to be confirmed or accepted by other research groups, however, and has not actually been tested against the predictions of standard galaxy formation models.